0F9Dn000000lXdZKAU is the Id of an existing Group
CollaborationGroupMember newGroupMember = new CollaborationGroupMember(); newGroupMember.CollaborationGroupId = '0F9Dn000000lXdZKAU'; newGroupMember.MemberId = [SELECT Id FROM User WHERE Name ='Emily Anderson'].Id; insert newGroupMember;
