You have to complete chapter 1 to unlock the bonus missions. Unlocking uptown is part of chapter one. Mystic falls is part of chapter two, which, according to this page, is going to be released in March. So if you finish chapter one by then, you can do what I've been doing and start the bonus missions. You get at least 20 XP for all of them, and 5 mystic coins for each one you finish.
You have to complete all of the available chapter mission to unlock the bonus missions, which means completing all of Chapters 1 and 2, and then some of Chapter 3. Uptown will unlock when you get to a specific part in the chapter missions when you need to go to that area. It is not possible to unlock Mystic Falls at this time.