Enhance your Crusader Kings II experience with the Persian Unit Pack. The Persian Unit Pack adds seven new, unique unit models for Persian rulers. Crusader Kings II explores one of the defining periods in world history in an experience crafted by the masters of Grand Strategy. Medieval Europe is brought to life in this epic game of knights, schemes, and thrones...

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.