Back to the Future: The Game is one of Telltale Games' popular episodic games. It follows the story of the famous Marty McFly and Doc Brown as they stumble through another adventure in time. It is broken into 5 episodes, and incorporates Telltale's unique spin on point-and-click games.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.