Lets see, first obviously you need to go to their website, next you need to log in using your Windows live ID (email account and password) in top right corner. Once you've done that you need to find the blue bar right below the BUNGIE logo in the top left corner, along that blue bar, (under the BUNGIE logo) it will say projects, roll over it with your curser and a long bar should appear. down this bar you should see downloadable content, under that is all the Halo 3 maps (Mythic, Legendary, Cold,& Heroic). Click on the map you want to download and it will take you to a different page, on that page it will say Download To Xbox 360, click that and it will take you to the Xbox.com website, scroll down until you see Download To Xbox 360 again click that and it should make you login again (same thing as before) but then it should have been added to your download que, next time you run Halo 3 it will automatically download to your maps. :] Enjoy!!