drag the models and materials folders into steam\steamapps\common\GarrysMod\garrysmod\
If they're not in addon format, putting them into this directory means going into the Browse > Garry's Mod directory of the spawn menu instead of the usual Addons or Legacy Addons folders
Just so you know
implying gmod hasn't been riddled with research since the beginning of the neolithic age
SFM's also caught this disease, but at least they're animated okay-ish, but the fact that they modeled...
that stuff is just kinda off putting to me