Booking multiple rooms?

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Hello! When Disney opens up the rest of 2021, I will need to book 3 rooms. In the past I have always done it by phone, but I’m thinking the phone lines might still be a bit crazy so I was going to book online.
What is the best way to “link” the 3 rooms to show we are traveling together?
Do I have to book each one separately and then call later to add the “traveling with”?
Or how would I add multiple rooms to my cart ?
Thanks