It is my understanding that only an owner may invite a person to become an administrator. If you are the owner - 1. Log in as Administrator.
2. Click 'Tools'
3. Click 'Invitations'
If the person is not already a guest fill in the
Invitation boxes at the top of the page.
If the proposed person is already an Invitee look down
the list, on the same page, for their name.
4. Click the little downward arrow in the box to the left
of their name and select 'Administrator'.
5. Click 'Save Changes' at the bottom of the page