Adding a Texture to an existing Aircraft

ok, my problem is that i dont know how to add a texture to an aircraft i have in my library. in the folder "AS365BH" (the aircraft folder i'm trying to add a texture to) it has subfolders; Model, Doc, Panel, Sound, and Texture. I'm trying to add a texture folder labled Texture.met for wyane Smith's VA NY Metro Helicopters. How do I do this????? Thanks for the help and if it is unclear or confusing let me know and i will attempt to clearify. Thanks again!! 😂