Hi!
To Install this skin you need to do this:
1. Unrar ''materials'' folder from your choice (black,blue,green ...)
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 pist_fiveseven and change it in pist_fiveseveg
and again you need to find w_pist_fiveseven and change it in w_pist_fiveseveg
4. Go an' play the CS:GO! ;)