The year is 2052 and the world is a dangerous and chaotic place. Terrorists operate openly – killing thousands; drugs, disease and pollution kill even more. The world's economies are close to collapse and the gap between the insanely wealthy and the desperately poor grows ever wider.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.