I think the app sets one for you after you signed up. There's the bit that asks whether you are a parent, how many kids you have etc -- think after that it generates the tagline for you, aaccordingly. (Correct me if I'm wrong anyone...) But you can change or delete it if you want. Go to "View Profile" and "Edit".
Yup. You can change it via the edit option. :)
Josephine Low