I guess you have some mods installed... So you already know this. But if not - here you go:

1. Download and install ME3Tweaks and Community Patch for LE3 (both links are present in the "requirements")
2. Use "ModManager Download" button in the "files" on this page.
3. Import mod to the library after it is downloaded.
4. Install it from the library. 
Yay, you did it!

Glad you asked!
There are several blocks of stuff mod provides:

0. Basic
Well, it is a mandatory part and the sceleton of mod itself. It allows you to have several romances instead of one, deletes some checks on commentaries from your squadmates and makes other basic setup running. With only this mod option on, you will feel like you have got a bunch of romances, and everybody knows about practically every partner you have. Get all the romances experience you can!

Options
All of these options can be found in the in-game menu (open your game, start or continue playing, press pause, look at the upper button in options wheel. Here it is, feel free to use!)

The good thing in in-game menu is ability to change settings at any moment of the game without any issues. 
We recommend  toggling jealousy, quietness, “other romances” permissions and "extended party" once when you begin your run, and have fun with other settings any time you want.
But, to be blunt, chance of wrecking the game by toggles is extremely low, so you can safely ignore advice. The worst thing you can get from it - some particular dialogs will trigger weirdly and/or non-consistently. No crashes, no black-outs, just a little weirdness.

Warning, chosen settings are stored in game save files, so you will need to set up configuration, that you want to have, at the beginning of every new run! You can easily change it later, but until you do it, game will run with default mod settings (all yes-no toggles set to no, no one chosen as a "party hookup" or "true love", and Liara will be on the couch)

Romances settings

 No jealousy
There is jealousy even in poly-relationship, it is natural to be, so it wasn’t removed mandatory, if it didn't break ability to begin romances. But if you hate the very idea of jealousy - here is the option removing as much of it as possible! Also it removed all the catfights.

• You can still begin jealous dialog by yourself, so the ability to smash Jacob's face is NOT a bug.
  

If any jealous lines were missed - you can report about it in a "romantic lines" bug report topic, and we will either think about removing it in future updates, or explain, why is this line kept.

Quiet romances
Do you feel like you don't want the rest of your team know who you are romancing? This option will remove any side mentions of your romances, that your crew makes (well... almost), and will remove (almost) all flirty lines coming from your love interests, that any other squadmates can hear. 
Avilable only if you turn "No jealousy” option on!

• This option doesn't affect some references to ME1 and ME2 romances - they are REALLY needed somewhere, so it seemed logical to leave them.
  For example - if Jack romance references were removed from her scenes in Gryssom, it would be unable to proceed with her ME3 romance afterwards. But there is a short-cut created in that dialogue, so it won't feel too revealing.
• James will always be aware of your romance with Cortez. He just can't be NOT aware. He most likely heard almost every dialog you have with Steve in cargo, and Cortez apartment scene in Citadel DLC requires James to know, so - yeah, it just makes common sense that he knows about this particular romance. 
• Also this doesn't remove the ability for you to show your feelings by yourself - so you can still kiss Traynor in Citadel DLC, and etc.
  

Subjective looks of one person were used to figure out, which lines are needed to be removed and which are not! Mind you, that person is also autistic, and definetely can not be perfectly correct with feelings. So if you are using this option and found something, that is not quiet enough for you, or if any replics or actions were missed - you can report about it in a "romantic lines" bug report topic, and we will either think about removing it in future updates, or explain, why is this line kept.

Choose your "True Love" option
Nessie gave names to settings and wants to stress out that in poly relationship there is no such thing as more and less “true-love” partners, and it is not a competition. This setting is named after the group of in-game variables, that are affected by this setting.These variables were named by BioWare devs.

This setting allows you to choose, which one of your partners will be there for you in culmination scene in the endgame, who will you wake up with after the party, and who will be there for you in a "goodbye" scene after the party (that's why Thane is also an option).
Basically, if game needs information, which one of your squadmates is your love interest, this option will let it know.
This option is also able to affect the choice of squadmate, who will come rescue you in Citadel DLC. (If your "true love" choice is present on Normandy at the beginning of DLC - they will come save you! Just ensure you pick whoever you wanted to be there, before entering the restaurant! If your chosen option is not available for some reason, Liara will come save you by default.)

Mod provides these priority romance options:
Garrus, Tali, Liara, Ashley, Kaidan, Traynor, Cortez, Jack, Miranda, Thane... Or none. You can just choose no one. By the way, "none" is default, so check settings before getting “true love” moments, otherwise you will get lonely Shepard in these moments.
(For example, "none" option can be used intentionally, if you want to see Joker's goodbye scene after the party)
Don’t choose the person you are not romancing. It is just pointless, as game additionaly makes sure that you have active romance with chosen person, before using data from this setting :)

         Tali/Garrus romance option
If you want to see these two have relationship, no matter if you romance any of them or not, this is your option to pick!
This option is dedicated to ones who love "Shalibrations" relationship (so, Nessie kinda made it for herself, yup). Also thanks to Audemus for this trio ship name :)

James/Ashley flirt option
If you want to see these two flirting, no matter if you romance Ashley or not, this is your option to pick!
This option won’t work, if you choose full hookup option for James (you can read abt it below), so you need to decide, if it will be Ashley or your femShepard involved in flirt :)

Party settings

Party hookup option
This setting works for femShepard only, and it allows your Shepard to wake up with James of Javik after the party, and fully overrides “true love” setting for this event.

You can either take full James option, or light one, there is description below, telling where is the difference.

• The full Lames option requires some conditions to be made besides turning option on:
  

1) Turn James option on before one-on-one meeting with him in apartment. 
2) Do all the vanilla stuff you need to do usually to wake up with James: flirt with him both when the apartment meeting with him is going on, and also on (rowdy) party

• The light James option only requires you to choose it any time before party ends, and run the rowdy party. You just end party, wake up - and boom, here is James nearby.
  

If you wanna see James wakeup scene and skip all the flirty-hunt stuff going before - light option is for you! 

As for Javik - just hit that button and run rowdy party!
Note! This mod completely overrides OFM feature for Javik hook-up, as if you use a manual button to decide if you want to experience his wakeup, i think there is no need in mission/relationship count checks added on top of it.

Couch neighbourhood 
Select who do you want to see near you on the group photo! It is now detached from love interests and can be regulated with a button! Share couch with anyone you like! The only non-avilable options now are Joker and EDI (who are already on the couch), and also krogan - they are way too big to fit on a couch like human-sized squadmates. 

If you don't work with this setting, you will get Liara next to you on the couch.

Expanded party
Don't want to choose between rowdy and quiet party? Well, don't! this setting will loop party, so you will have:
Phase 1 - Quiet phase 2 - Quiet phase 3 - Rowdy phase 2 - Rowdy phase 3.
Together these sets will allow you to experience the most full party avilable without any save-loads included.

in version 2.1.0 - none.

Current version is patchless, but we are working on this, and one day it will be patched. Then… 

This mod will be compatible with:

Take Earth Back
Expanded Galaxy Mod (invites and photo will use “true love” setting. Wanna change photo and invite option? Swap that setting! If it didn't help, leave your cabin floor and then come back)
More Gay Romances
Optional Flirting Mod (James full hookup option will only work with this mod if you flirted with him troughout the entire game)
Choose Your Friend (CYF will always override my mod, when it is on. Also any person, who comes to save you, will act friendly and not flirty, before the rest of your crew comes to apartment)
Padme's cabin additions and memorials 
Easy Pull-up Competition mod

Also mod has an in-built compatibility for Community Patch LE3 and is definetely compatible with Multiple Romances for LE2 (obvious, but still needed to be mentioned), so you can import your polysexual Shepard from LE2 and not experience any trouble!

If you don’t know if PRM needs patch to work with some particular mod, ask us, and we will make a check!

This mod is definetely NOT compatible and not going to become compatible soon:
With Starchild-be-gone. Well... Not exactly INCOMPATIBLE. If you disable setting for dream #3 while installing SBG, it will work fine.

Issue: game can pick incorrect romantic partner to appear in dream sequence #3. This dream might also be incompatible with future features, that are in development right now. 

I wanna more patches! I found mod/i have a mod in need of patch to be compatible with yours.
Great, then let's make more patches - we love compatibility!
If you want to use this mod with any other mod you are not sure it is compatible with - ask us, we will check it up, tell you results and maybe create a patch, if needed!
If you create mod or already have any mod, that can conflict with PRM - inform us, that you are making a patch (no approvement needed, just inform us and feel free to work on it) and/or ask us to develop one!

Not yet for culmination, and concrete no - for party. Option for culmination is taken in development by Trench, but it requires time and is basically hell to implement. And there are several reasons why it wasn’t developed by Nessie:

0) (tech one) the end of each single scene triggers the next plot phase. Too problematic to edit.
1) (plot one) There is a little time both after party and before Cerberus attack. It is illogical to have several scenes in this case - there is no time for it.
2) (is it needed? - one)The wakeups at party are pretty the same exept one or two voice-lines, coming from partners, and we don't think it is actually needed to experience them all at once - you will be tired of the repeating sound samples and content very soon, if these scenes are running in a row. Believe us, Nessie tested “true love” setting on this scene, and it gets very repetitive very fast.

Be careful - there is no culmination for Thane (for obvious reasons), Jack and Miranda in vanilla. This mod doesn't add them either. Make sure to check “true love” settings before you start Cerberus attack!

Nope. You still need to follow the romance rules to be able to romance the ones you want to - be nice, flirty, not dump them and so on. 
Also this mod doesn't add ability to ignore your gender in romances! 
FShep/Miranda and FShep/Jack mod is on a patch list, so it will become compatible with PRM once patches are up to date.
If you want to romance someone else and there is a mod allowing it - tell us about this mod, as this type of mods requires patching for PRM compatibility. Once it is patched, you will be able to romance that person and not only them, simultaneously.

Well... Yes and no. 

• Text localisation: there are English (INT), German (DEU) (no party), Spanish (ESN) (no party), Italian (ITA) and Russian (RUS) translations avilable right now. Other languages are automatically replaced by english.
  

What text is affected by this mod?There are two text changes made for one dialog wheel (chat with Thane in Huerta before the Coup). Also there is some text in in-game menu. It is not that big amount of text, it is tolerable even in non-translated condition, so don't be scared, it won't make game process difficult or uncomfy, no subtitles in any dialogs are affected by mod!

• Sound localisation: Mod is fully localised for english sound. As for the other sound versions - the very basic setups are not dependent of language, so you will definetely get an ability to have most of romances. Also true love option will mostly work okay (But true love option won't work for Thane, and you will get automatic true-loved Cortez, if his romance is activated. Somehow.). The "no jealousy" setting will also work (not completely though - several glimpses will remain.)
  

The problem is this mod doesn’t only change audio-independent content. Removal of any any small issues was performed on english localised files (i.e. dialog trees with audio files attached) - for example, there were refusals of some characters (like Allers) to have romance, if you have any another romances, automatic priorities of choosing, who is going to say romantic stuff, if it is a crowded scene... And the entirety of in-game settings (besides “true love”) is running on localised dialog edits, too. It is not dangerous, no black screens, no game crashes and save file obstrustions, but it is sloppy, can be a mess to witness, and definetely can’t give you full PRM experience. But you can still opt to play with other language of audio, we just don’t recommend it due to reasons named prior.

Definetely not, if we are doing it for ourselves.

• As for text - it is impossible to translate text into languages that person doesn't know. If there were single words only - maybe, but not the complete sentenses, not the instructions. If you want to offer your help with translation to language which is not covered yet - feel free to contact us! We will happily give you file to translate and help, if it is needed!
• As for sound - mod caused enough suffering with the english one, and repeating this three more times is unbearable. But if you have skills in sequence and dialog editing - feel free to make this for yourself. Remember, you have our permission to do any alterations for your personal use. Contact us if you created it and want to get it published.

Mount 9998
Added conditionals 25353-25361
Added plot Integers 12479, 12480
Added plot booleans 31500-31520
Added tlk id-s 9896498-9896575 (PI included here)
Overwritten tlk id-s 639083, 639084

If you need more info, contact us!