This addon is a theme. You need to extract it to your /themes folder to install it.
Custom Vanilla Skins. - Game
If you use this theme click LIKE IN this forum thread Game is a PREMIUM theme we are releasing to the Vanilla Community for Free. No support whatsoever, unless you pay :) If you want to see it working, goto www.vanillaskins.com/game-forum
We are available for coding any projects you may require and creation of custom themes. Follow us on Facebook and Twitter.
New for Q1/2 2012 new themes ( freebies ) for Vanilla ( Paying customers ) watch this space.
Do not use the ABOUT.php file ( first one you see ) this is needed to be able to upload to Vanilla Forums, instead open the Game Folder, and read the readme.