I did this because I just recently found out how to.
Download Modio from-
http://www.game-tuts.com/community/modio.phpGet a flash drive at least 8 GB big.
Search for your game on the application.
Download the mod.
Before you continue, take your 8 GB flash drive and format it on your xBox.
You can do this by going to your xBox home screen.
Now go to system Settings>Memory>USB Memory Stick>
Now click the top button.
Wait for it to format your drive for xbox compatibility.
Now download your mod to the flash drive from your computer.
Plug into your xBox and ENJOY