I am helping my friend make a game that uses 3d models, and I was wondering how you add a different texture to each side of a cube.
welcome to the boards @LeWolfYT!
…as you can tell, the forums are dead. 
for simple little questions like these though, i’d suggest you just ask on the discord server channel. Someone’s usually there, and if even no one is in the specific Heaps channel, they’re hanging around the server somewhere…