Simply head into Walmart purchase Xbox One Forza Motorsport 5, and $8 of M&M's (see participating products here), and text a picture of your receipt with the code M&M to 811-811.
The graphics for this game are ah-mazing! Xbox One has really stepped it up with Forza Motorsport 5.
Make sure you also check out the M&M's Pixel Art Contest, you can win an Xbox One, Forza Motorsport 5 and the perfect gaming snack M&M's. You can enter up to 3 times per day, so get to designing your M&M pixel art. See official rules here