how to change my account to my husbands?

Hello. I have been using T-mobile for a few months now, and now that I'm married, I want to put my line onto my husband's tmobile plan. The thing is, we're in different states at the moment, but he sent me all of his information to transfer it. I just don't really know how, though. I want to keep my number as well. Do I need to go in store for this? Does he have to be in person with me, or since I already have a number and all, can I just do it online? If I can do it without going in person, that would be great.