Prototype is the first of two games, and let's the user take control of Alex Mercer as he fights to stop the viral outbreak known as BLACKLIGHT throughout Manhattan. Alex is himself infected by the virus, which has given him special, mutant, abilities that will evolve with time and aid him in stopping the virus.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.