Instructions
Log-in to your Xbox Live account on the Xbox 360.
Access the "Game Marketplace" in the "My Xbox" section of the dashboard.
Select "Game Add-ons" in the Game Marketplace.
Choose "A-Z Titles," then select "F" from the list.
Navigate down to "Fallout 3," then press "A" on the controller.
Highlight the content you want to purchase, then press "A" on the controller.
Choose "Confirm Download" from the list of options.
Confirm that you want to purchase the DLC using Microsoft Points. If you do not have enough points on your Xbox Live Account, you will be prompted to purchase an appropriate amount by entering a credit-card number
Launch "Fallout 3" once all DLC has been downloaded. The DLC packs are automatically installed once downloaded and can be played immediately.