MDE is “My Disney Experience”
Go to the main DisneyWorld page (or download the app), and browse over to ‘My Plans’ under ‘My Disney Experience’. If you haven’t already created a Disney account, you should be able to do that at this point. Then click on Add Plans -> Resort Hotel Reservations. At this point try putting in your reservation number.
Once you do this, your OKW reservation should show up, and then you can customize your magic bands.