You go to the county court house and go to the county clerk's office. Our daughter did this as a present for her "real" daddy's birthday. Her other father was mean and abusive and her newer father has been "hers" since she was 4. She, all on her own when she was over 18, went to the court house and did it (we were working in Asia at the time). She even got to see the judge personally because her Daddy was an officer of the court for years and he wanted an update. You may have to post, in public places (ask the clerk's office what that means) and our daughter posted at the court house, went across the street and posted at the library (where I had been on the board for years) and when asking permission the head librarian realized who she was and took her into the basement (snack room) and asked the newer people if they would let the "older" emplyees have it for a time, and someone had a birthday cake and they all partied for a half hour and caught up. What a positive experience!
Hope your experience goes well.