Cant install " CM10 Alyx NPC Pack "

Hello,

First all Im sorry if its an off-topic question !
anyway… I dont understand how to install addons !
i tried lot ways… and it not work !
I’m trying to install " CM10 Alyx NPC Pack " and i cant… can somebody tell me how install it ?

  1. You can’t install addons you can only download them.
  2. Download WinRar or 7-zip
  3. Download it and put in C:\Program Files\Steam\steamapps<username>\garrysmod\garrysmod\addons
    Program Files (x86) if you have 64 bit

If they come with an “info.txt” file, put them under addons. (C:/…/garrysmod/garrysmod/addons)

If there is no “info.txt” file, put them in the main folder. (C:/…/garrysmod/garrysmod)

Ok… by the way this is the addon
http://www.garrysmod.org/downloads/?a=view&id=100456