You will be able to manage your Groups in the "Create + Manage Group" page. Here, a table will display all of your groups.
To delete a Group, click the trash can icon in the right hand column next to the Group you want to delete. You will have to confirm this action and click the pink "Yes: Delete this Group" button.
Note: You will only be able to delete a Group with no active invites. If you must delete a Group with invites, first delete all of these invites in the "Your Guests" table in the "Track RSVPs" page. Then, navigate back to the "Create + Manage Group" page to delete the Group.
To edit a Group, click on the Group Name in the table. Here, you will be able to edit part of the Group.