Help with texturing this gun

I have the model and textures premade but i cant’t get it lined up correctly

The guy who posted these said that i need to “fix smoothing groups” and “detach merged sub meshes” but i don’t know what that means exactly.
Even a quick translation for what those mean would be super helpful!

b u m p e r i n o

No one reacts because there is simply not enough information to solve this problem. Attaching a blend file would be most helpful. I would say, the model is not unwrapped, from what I see on your screenshot.

yer agreed. Need a blend file to help on this one