That's straight forward. You go to court and have your name legally changed.
https://www.tn.gov/safety/article/dlnamechange
One thing I'd recommend is to immediately go to the clerk and get a number of "true copies" of the order (these will typically be embossed). You'll have to show them (and possibly leave a copy with) various other entities to prove you legally changed your name. Same thing with marriage certificates when you get married. I started with a half a dozen and I think I only have one left.

