The MM event reservation can't be linked to
MDE, you could add a "Note" if you desire.
On the event day, you check in at a designated spot at the theme park entrance where you need to show your Digital Membership Card and a Photo ID. You will be issued the event specific wristbands and any food coupons. Once you have your event wristbands, you can enter the park without needing separate theme park admission. If you are already inside DHS, there should be a designated check in location which should open at around 2 pm (based on what they did for the Epcot MM events).
Pre COVID they used to offer event check in at the
DVC Resorts. Not sure if this will return.