ooookaaayy!
PC user?
My Documents > Sports interactive > Football Manager 2012 > Then, Create a Folder called "Graphics" > Go into your newly created "Graphics" folder > Then create a new Folder in that one called "Facepacks"
Then what you'll wanna do is unzip the .rar to that new folder. You'll need winzip or 7zip (I suggest 7zip much better) to unzip that .rar file.
Once you've done that, You are going to go into your game and go to your preferences and make sure that you have the "Use Skin Cache" box UNticked. Hit confirm
Then your game will "Refresh" its self and you'll have all the wonderful ugly mugs that are the chelski team