To edit or delete a pre-existing group, navigate to the 'Groups' page on the passport from the list on the left of the page. Next, click on the edit button next to the group you are looking to change.
Once this has been done, you will be able to change the name of the group or delete the group from the page.
You can view a list of all the users that are assigned to a group by clicking on the view button next to the group, you will be able to remove all the users of a group from this list.