It is the year 2938. The long wished-for encounter of the X Universe and the Earth holds both joy and sorrow for the people. Despite flourishing trade, the clash of the diverse races, cultures and life forms creates new tensions, mistrust and open conflict that need to be overcome! Experience the brilliant climax of the legendary X-Trilogy , and take your place in the history of the X Universe.
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.