This is a texture mod, so it should be activated as any other Texture mods for Minecraft:
While in game press Esc -> Options -> Resource Packs -> "Open Pack Folder"-button and put downloaded .zip-file in that opened folder. "Java xray-189-Jana-161492..." should appear in "Available" column on the left. Hover mouse over it and click on appearing arrow to move it to the right "Selected"-column. It will give you warning about incompatibility(just agree with it) and "new" textures will take over.
No need to restart the game(just tried right now on 1.21.1 Java version and it works, can see-through in ground for Coal and Copper). P.S. never used mods before, just CheatEngine to multiply gathered resources(primitive search is not working anymore because adresses are changed by Java too fast)
4 comments
While in game press Esc -> Options -> Resource Packs -> "Open Pack Folder"-button and put downloaded .zip-file in that opened folder. "Java xray-189-Jana-161492..." should appear in "Available" column on the left. Hover mouse over it and click on appearing arrow to move it to the right "Selected"-column. It will give you warning about incompatibility(just agree with it) and "new" textures will take over.
No need to restart the game(just tried right now on 1.21.1 Java version and it works, can see-through in ground for Coal and Copper).
P.S. never used mods before, just CheatEngine to multiply gathered resources(primitive search is not working anymore because adresses are changed by Java too fast)