Event Management -> Guest Groups
Start by clicking on Event Management on the left hand side menu and click on Guest Groups:
Click on the Guest Group name to show the Group details:
Click on Guests located on the Guest Group page to display the Guests who have already been added and add new Guests:
After clicking on Add Guest, a new window will show you a list of Guests that can be added to the Group. From here, you can select Guests to be added and click Add Selected Guests:
All Guests will then be displayed in the Guest Group details page after being added and you have successfully added a Guest to a Guest Group: