Beginning with update 1.9.0.0 you now have two options for equipping yourself with Gunslinger weapons. 

Option 1 - Scaling Gunslinger Weapons
Scaling gunslinger weapons will be in your inventory on character creation and additional types (rifle, shotgun, pistol) are available in your armory chest. The armory chest spell is granted to you at level one and will be on your hotbar. Just click it and a temporary chest will be summoned in your inventory. From the chest you can grab a 2nd pistol, or get a rifle or shotgun. The scaling weapons will have a passive effect on them called "Stalwart". The weapons will automatically gain a +1 increase to attack and damage rolls every 3 levels starting at level 3 (+1) and going up to level 9 (+3).

Option 2 - The Gunslinger Forge
The forge is available in your armory chest, along with template weapon(s). The template weapons are clearly labeled as such and will just be white quality weapons of each type (pistol, rifle, shotgun).

To use the forge you just open it and place the template weapon in one slot and a looted weapon in the other slot. Click the combine button in the center and it will output a new weapon with the looks of the template weapon and the abilities/stats of the looted weapon.

Some looted weapons will not combine with certain template weapon types. You can generally expect looted weapons to follow these rules.

• 2h staves will combine with Mage/Saint rifle and shotgun templates
• 1h caster melee weapons (there are only a few) will combine with Mage/Saint pistol template
• 2h melee weapons will combine with Gunzerker Gunblade template
• 1h versatile weapons will combine with Gunbreaker Gunblade template
• 1h finesse weapons will combine with Deadeye Gunblade template
• 2h ranged weapons will combine with Gunslinger rifle and shotgun templates and Deadeye sniper template.
• 1h hand crossbows and 2h short bows will combine with Gunslinger pistol template