Textures rely on UV unwrapping to determine where they show up on a model. And textures themselves aren’t applied to obects, but are members of materials that are assigned to objects. Go to your materials panel, enter edit mode, select your face, and assign the desired material. It’s likely you’ll need to UV unwrap your model before getting the results you want though.
Thanks for you help sir, I’ve tried going to the material tab and I saw the texture I want in my preview so I highlighted what I want and I assigned it but nothing happened. But thanks so much for your help
Check the mapping mode on the texture tab, are you using “generated” or “uv”? If you are using UV mapping, you probably should watch a couple of tutorials on UV mapping - or (something like): change from default to “UV Editing” screen layout, then select each face you want to texture, press U to unwrap and choose the texture in the UV window. By the way, the blend file you posted doesn’t appear to contain any materials or textures.
Problem geometry: extra faces. To fix in edit mode select all remove doubles, select none, select interior faces delete faces only.
No lamps. Add sun.
No materials. Add material.
No textures. Add new texture. I gave it a color grid, saved it, and packed it so you could see it on your end.
No unwrap. In edit mode, select all, hit U, select smart UV.
The rest hopefully you can see in the file attached all the above has ben done, so th instructions above are for you to fix the file you have not the file I am sending!
In the texture panel you can change the current texture to the one you want that is on your computer by using the open button next to the name.