You’re automatically put into your Town Group based on the address you used upon signing up for your Howl account.
To learn how to change it click here (profile management page). Your Town Group consists of any Howl user that lives in your zip code.
Posts to your Town Group can have a location, if they do, they will be visible on the map only for those who are a part of the group. It will also show in your group feed whether it has a location or it does not.