Join the Doctor as his companion in an out-of-this-world adventure through time and space. You will need all your wits and courage to outsmart and defeat some of the Doctors' most storied enemies like the Daleks, Cybermen, and the Vashta Nerada. Explore the universe, and even see the inner workings of the TARDIS!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.