Instructions
Insert the pen drive into an open USB port located behind the flip door on the front of the Xbox 360 console, then power on the console.
Highlight the "System Settings" menu option in the "My Xbox" section of the Xbox dashboard, then press "A" on the game controller.
Highlight "Menu" in the list of options, then press "A" on the game controller.
Highlight the storage device that has the XBLA title you want to install, then press "A" on the controller.
Select the "Games" folder, then press "A."
Highlight the XBLA game you want to copy onto the pen drive, then press "A."
Select "Move" from the list of options, then press "A."
Choose the pen drive from the list of storage options, then press "A" on the controller. This will install the XBLA game on the pen drive.