When I try to add a texture to a gun it seems to just change the general color and not actually apply the texture. Am I doing something wrong?
Your must be using a material and not a UV Map. What modeler are you using? I’m assuming blender since it’s really the only free one out there. basically, a UV map is a 2D map of your object, and when applied wraps to the object in 3D space. Watching this video can help:
more information here:
You must define the UV map to link each vertex of the gun to an specific point of the texture - that’s called UV mapping. This isn’t Unity stuff: it’s part of the model file, and you usually create it in your 3D model editing software (Maya, Blender etc.) with help of a 2D image editor (Photoshop, Gimp etc.). There are lots of tutorials specific to each 3D editor in the web - just look for something like how to UV map.
Basically, you must unwrap your model in the 3D editor: the model faces are projected on a flat surface, and you can paint it in an image editor. The 3D editor then calculates UV coordinates for each vertex (XY pairs in the range 0…1) and creates the UV map.