In Deus Ex: Human Revolution you play Adam Jensen, a security specialist, handpicked to oversee the defense of one of America's most experimental biotechnology firms. But when a black ops team breaks in and kills the scientists you were hired to protect, everything you thought you knew about your job changes. At a time when scientific advancements are routinely turning athletes, soldiers and spies into super-enhanced beings, someone is working very hard to ensure mankind's evolution follows a particular path. You need to discover why – because the decisions you take and the choices you make will be the only things that can determine mankind's future.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.