With the App Editor Panels multiple groups can be added to your Fanapge. Just connect on this page with "Lets Go" and grant the requirted Permissions to access your Groups and install it on your Fanpage. You can change at anytime what group you would like to connect by simply turning the switch on/off for the Group. Every Page can hold individual Groups, befor you turn on Groups you have to enter the name of your Page to select one.
Why you should conect Groups to your Fanpage ? With Groups for Pages you give your fans and community a open place to talk about your brand and topics, a natual way to Invite intersted Friends to your community.