How to register a service which is part of a group on ArcGIS Online

Has anyone figured out, or is there any documentation available for how to register a service that is part of a Group in ArcGIS Online? I am able to reference any of ESRI's services following the instructions in "How to Set Up an ESRI Geoportal Server" but we have published services to several groups on ArcGIS Online which require group membership to access. How does one register services in groups like this?

Doug Olcott
GIS Software Engineer
ISD - GIS
Santa Clara County