Instructions
Log in to your Xbox LIVE profile, PlayStation Network profile, or start the game disc on your PC. On the Xbox 360, go to the "Game Marketplace" menu. On the PS3 and PC, go to "Add-ons."
Select "Explore New Games" if you are using an Xbox 360, choose "Add-Ons &Extras," and then select "Fallout 3" from "Titles A-Z." Once inside the "Fallout 3" menu, choose "Extras" and select "See All Extras."
Select "Disk-based Add-ons" if you are using a PS3 and then choose "Fallout 3."
Select the DLC pack you'd like to install from the list on your Xbox 360, PS3, or PC. Your options will include "Operation: Anchorage," "The Pitt," "Broken Steel," "Point Lookout" and "Mothership Zeta."
Select the "Confirm Download" option on your Xbox 360, PS3 or PC to install the DLC pack to the game.