More specific info please? But usually the files need to be unzipped (maintain folder structure), or you can manually unpack them, but you need to know where they go.
I believe the 'hi-res' files should normally reside in the textures2 folder of your Orbiter install, or at least thats where my moon, earth, clouds, mars files are.
As far as making them work, if they are in the right place, Orbiter should take care of that all on it's own.