An ancient evil lurking within the Master Emerald has been unleashed from its slumber by the devious Dr. Eggman and is on the verge of becoming the ultimate monster using the 7 Chaos Emeralds. Only Sonic and his friends are heroic enough to put a stop to Dr. Eggman and his evil minions.Go to: http://store.steampowered.com/ and download STEAM client
Click “Install Steam” (from the upper right corner)
Install and start application, login with your Account name and Password (create one if you don’t have).
Please follow these instructions to activate a new retail purchase on Steam:
Launch Steam and log into your Steam account.
Click the Games Menu.
Choose Activate a Product on Steam…
Follow the onscreen instructions to complete the process.
After successful code verification go to the “MY GAMES” tab and start downloading.