After you purchased Google Maps Engine, you or your deployment partner set up a Google Group for administrators in your Google Maps Engine Platform domain. This group is listed in the Google Admin console under Groups.
By convention, the name of the group is gme-administrators@gme-your-domain. For example, if your company is Altostrat and its domain is altostrat.org, the group would be gme-administrators@gme-altostrat.org.
To add another administrator for Maps Engine, add the person to that group. Remember that administrators have access to all data, layers, and maps in Google Maps Engine.
If you want the new administrator to be able to add or remove members of the gme-administrators group, the new administrator must have a user account in the GME domain.