If you have purchased the Empire : Total War Special Forces Edition or received an exclusive pre-order unit via participating retail outlets, you will need to connect to the internet, redeem your code through Steamworks and easily unlock your units for use in game.
1. Install Empire and the Steam client as per instructions included with the game.
2. Launch the Steam client and select "Activate a product on Steam..." under the "Games" menu.
3.Go through the Steam Product activation wizard, entering the product code when prompted.
4. The units will then become available in Empire’s single-player campaign/ battle modes and multiplayer under certain conditions - see "Where do these units appear in the game?" article.