Hi!
To Install this skin you need to do this:
1. Unrar ''materials'' folder from your choice (Red Camo,Savana,Simple Black ...)
to Steam/steamapps/common/Counter-Strike Global Offensive/csgo.
2.Next you need to go to csgo and open  pak01_dir.vkp (first make backup folder of that file)
with Notepad ++.
3.And you need to find rif_aug and change it in rif_auf
and again you need to find w_rif_aug and change it in w_aug_auf
4. Go and play the CS:GO! ;)