Yes, correct you have to use Horizon to get your maps working (let me show you how:)

You need:

• a PC or laptop
• USB flash drive with at least 1 GB of space. Note that it should also be USB 2.0 or higher
• Your Xbox 360 with Minecraft as a disc or downloaded (of course)

Step 1: Plug in your USB flash drive into the Xbox 360.

Step 2: Download your map(s) on your PC.

Step 3: Download Horizon on your PC.

Step 4: On your Xbox 360, go to System Settings > Storage > (your hard drive) > Profiles. Then move your profile you want the map(s) on to the USB flash drive by pressing A on the profile and press 'Move'. Press the USB drive to move it to there and the process should be very quick.

Step 5: Eject your USB drive and insert it to one of the USB ports in the PC.

Step 6: Load up Horizon. If it needs an update, it should be quick.

Step 7: On the right side, the Device Explorer should already pop up if you have inserted the USB drive already.

Step 8: Click the little arrow next to the 'Gamer Profiles' button. Now press and hold your profile to the blank, grey screen.

Step 9: Open file explorer and locate your map(s). Then drag and drop it to the blank, grey screen in Horizon.

Step 10: Now copy and paste the Profile ID to the Profile ID on the map. Do the same with the Device ID and the Console ID. When you're done, click the red button that says 'Save, Rehash, and Resign' on the map. Then click 'Save to device' on the map as well and click your USB drive. When done, close up Horizon.

Step 11: Eject your USB drive safely from the widgets next to where the time and date is and click on the icon with the USB drive and a tick on it and click Eject. Now pull out your USB drive!

Step 12: Put the USB drive into the Xbox 360 and move your profile and the map(s) to your hard drive (or wherever you keep all your stuff).

Now play Minecraft and your map(s) will be there! And don't forget to eject your USB drive!