One of the great things about minecraft is the ability that you can create a map and then hundreds or maybe thousands of people can play that map, and there is no exception with minecraft xbox 360.
How to Install Minecraft Xbox 360 Maps:
1. Download the minecraft xbox world
2. Plug the USB into the Xbox 360
3. Movethe Xbox live profile from your xbox Harddrive to your USB.
4. Plug your USB into your computer.
5. Download Horizon: http://www.xboxmb.com/horizon/
6. Load up your gamer profile (It should open on the right side)
7. Right click your profile and Inject the world download file into your profile.
8. Rehash & resign.
9. Plug the USB into the Xbox 360
10. Move your Xbox live profile (And the Map) from your USB back to your xbox Harddrive.