All copies of Battlefield 2 purchased on Steam come with the Special Forces expansion, as well as the Euro Forces and Armored Fury mini-expansions.

To access them, please see the following instructions:

1.Open Battlefield 2 and log in to your Battlefield 2 account.
2.Once logged in, click the Community Button, then Custom Games.
3.Select the "xPack" game, which should be "Battlefield 2: Special Forces" and click Activate in the lower right. You will then be asked to restart the game.