You could have it done professionally, or buy a kit at your local home improvement store.
Both above ideas are good, just know they are,temporary, will peel once scratched, even the prof done ones. I have a wonderful old claw foot and have to have mine done about every 4 years. About $350. each time. If it's not that bad, don't do it. Once you do you have to keep doing.
call a refurbishing tub company and they give you a great job. They are professionals and you'll get a guarantee. I've had it done and was very happy with the results.
Not knowing what style of tub you have I will give you several videos to choose from. Good luck with it, Tami.
Rustoleum or Homax tub and tile paint kits. Proper prep is the key. Take no shortcuts.