They don't require an appointment but I went last week to get mine and didn't take the proper ID to obtain the Real ID (the star) if I could figure out how to post a picture I would post the required documentation list they gave me. If you have a passport, that's all you should need, if there's a name change involved be sure to take marriage certificate, divorce decree etc. It is Not like a normal renewal! I went for the star and a renewal and only left with a renewal.
Check out the info on the tn.gov site
It's quite similar to a normal renewal of the license. Simply go to the center and make a request. Do try and find out if you require an appointment first, though, because of covid precautions. You can call ahead for that
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