You must be Group Administrator of the Personal Group to add and remove members of a Personal Group.  To add and remove members of the Personal Group, from the Personal Group page, click on Group Administration > Manage Group Members, here you will see a list of your Friends on Clubster, then search and check the box of member or members you wish to add to the group, and click Invite Selected Friends.  These Friends will now be members of the group. Only Friends of the creator of the Personal Group can be added as members of the Personal Group.