Connect as Admin
Administration Menu > networking > Peers > Select a peer > Services tab

the SSO (Identity Provider) section includes a checkbox with the help text:
Publish this service to allow your users to roam to the Jeromes Moodle HEAD mnet Moodle site without having to re-login there.
the SSO (Service Provider) section includes a checkbox with the help text:
Subscribe to this service to allow your users to roam to the Jeromes Moodle HEAD mnet Moodle site without having to re-login there

These two checkbox seems to end up to the same functionality.
It could need some rewording or merging the two checkbox into one.

Note for QA tester: in order to setup a Moodle Networking, follow the Moodle docs: http://docs.moodle.org/en/Moodle_Network