How do i share calendars with servers

I am having problems sharing a calendar between a Windows user and a Mac user. When the shared calendar is open in Mac, there is no way we can pick a specific calendar aside from the primary one?
The Outlook 2011 does not permit adding shared calendars to your own view.
Even when the Windows user is invited.
So I don't think that it's an issue of permission because the calendar opens up in OWA on Mac without problems.
How do I do this in Outlook 2011?
