To access a shared folder that isn't one of the folders listed on the File |
Open | Other User's Folder dialog, the mailbox owner needs to grant Reviewer
permission to the root of the mailbox, as well as appropriate permission on
the folder.

The user who needs access then goes into Tools | Services, brings up the
properties for the Exchange Server service, and on the Advanced tab, adds
the mailbox.

After that, the user will see in the folder list all those folders in the
secondary mailbox to which he/she has access and can add any of those
folders to the Outlook Bar. See
http://www.slipstick.com/outlook/links.htm#addtobar.

I have a sub calendar in my Outlook calendar. I have shared the sub folder
and given the appropriate user access permissions, and checked Folder
Visible. But when that person tries to open the folder it is not visible.
Only Calendar, Contacts, Inbox, Journal, Notes and Tasks are visible.