Any Personal or Closed groups that you have created you can edit or delete.
Double-click on the group name to open the group up. 
Once you are inside the group, you will see all of the members in the group.
To add additional members or remove someone from the group, click the pencil icon to go into editing mode. 
The "Edit Group" screen will open and allow you to add additional member(s) and/or delete members whom you no longer want in the group.
When you are done, make sure to click "Submit" to save your changes. 
To completely delete a group, click on the trash can icon in the top right corner.
