How do I un-join a group?
When you click on your name (or avatar’s name) in the navigation bar you will come to your personal page. The top row of your navigation bar starts with the word Activity. In that row of choices you will see the word Groups followed by a number. Select Groups, and a list of all the groups you belong to will be listed.
Find the group you would like to un-join and click on the box Leave Group. That it!