To delete a group do the following:
On the Users or Workspaces tab click the Manage groups icon. This will then open the groups window.
Select the group you would like to delete and click the OK button. This will open group Details window.
Click the Delete icon. This will open the Delete group window.
This will allow you to delete the group, users associated with this group, and workspaces associated with this group.
Once you have selected what you would like to delete click the OK button.