1. Click here to register
2. Take the code you receive via email, and go here - http://www.medalofhonor.com/beta
3. Login to your EA account, or create one. Enter your email beta code, and click redeem.
4. You should now have an XBOX Live Marketplace code. Enter that on your XBOX 360 under "Redeem Code" on the Marketplace blade.
5. Download the Medal of Honor beta and enjoy!