Joined a community by accident or just looking to unfollow a community you have joined?
1. You must first make sure you are not currently viewing that community. You will know because of the color the app is in should not match the community you want to leave.
2. Once in another community:
You can click the crown or Explore button and see the list of Communities you have and have not joined. To the right you will see a "edit" button.
Click that and red "x's" will come up next the communities you have joined. Then you just click the "x" to leave it.