The Sonic 4 Saga continues in Episode II with the return of a beloved side kick and fan-favorite villains! Following the events of Episode I, Metal Sonic has returned to form an alliance with Dr. Eggman! To face this new evil, Sonic will have to call upon an old friend to help him save the day!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.