I'm assuming you rented points to your friend. They just need the reservation number and their last name (lead guest). Then they can match up the guests to whoever is in their MDE. You add ME online for DVC. The owner has to be logged in to do it.
If you aren't the owner and rented the points and they are staying with you, then yes, you need to add them in MDE and match them up. whoever is the lead guest has to match up all the other guests. You have to ask the owner to request ME.