A new detailed North American Campaign Map expands the Empire: Total War experience, with 5 brand new American Indian factions, new units and technologies. Experience battles in the new Warpath Campaign and lead one of the 5 new factions in an epic war to defend your lands and drive out the invaders. Or take these units and their unique strengths into multiplayer battles.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.