Hi Dan,
Actually, that's a mistake in our documentation -- Shibboleth support hasn't yet been ported to OCS, and I will fix the documentation to address this shortly. I just reported this as a feature request: see
http://pkp.sfu.ca/bugzilla/show_bug.cgi?id=4224, and please feel free to CC yourself for future updates. I've also linked to the original Shibboleth bug report in that report, which includes the original code changes for OJS in patch form; it may be possible to take these code changes and work into OCS. (Unfortunately, since there are changes to the core codebase, it's not a simple matter of copying the plugin from one system to the other.) If this is something you might be able to take on, please let us know, and we should be able to give you some help.
Cheers,
James