How to import custom models/textures into CS2

[Antferny]

I was told that I could import models/textures from other games like Garry's Mod that I can use in my map in CS2. Was told to use gmad.exe which I did but I have no clue where to put the two files that I extracted using gmad.exe which was a materials & models folder. Is there another way to import custom models/pictures/textures etc. that I can download and put into my map?