Call of Duty: Ghosts takes place following a catastrophic event that changed the global balance of powers in the world. As a result, the United States is no longer recognized as a superpower. Ten years after the event, an unseen enemy emerges as a threat, but the remnants of US special forces from every branch came together to create an elite group of soldiers known as the "Ghosts", who are determined to eradicate all threats to protect the weak and the remains of America.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.