To make a Business Page an Admin of a Group, you must Link it.
Go to Group Settings
Scroll down to Manage Advanced Settings
Click pencil icon for “Linked Pages”
Choose the Business Page you wish to be an Admin of the Group
Refresh Networks in CinchShare, find the page nested under the Business Page section.
If you can’t seem to link your page, try the following in Facebook:
Leave the Group as your Business Page
Ensure that you have Profiles and Pages allowed to participate in the Group.
If your Group does not show up in CinchShare after a refresh
That means Facebook hasn’t sent us the signal yet that you have added the Business Page. You can wait a few minutes, or manually link the Page to the Group. Here’s how:
Go to your CinchShare Networks page and go to your Pages section
Click this icon for the Page that the Group was created under