To set an Administrator or Manager in Reporting Groups, select a group then click on Edit under Reporting Managers and Administrators.
On this page select the members who you would like to be as Managers or Administrators, then click on Save Changes.
You can also see from a glance who is an Administrator or Manager on the group's page. Under the Reporting Managers and Administrators block there will be an image with "M" or "A" to designate if they are a Manager or Administrator respectfully.
To learn more about the Manager and Administrator roles please see User permissions in CollaborNation.