To share a folder:

1)    Right-click the folder to share and select Properties
2)    Select the Permissions tab at the top
3)    Click Add...
4)    Find the persons name you want to share the folder with or type it in the search box, click their name, then click Add in the bottom left, then click OK
5)    Click the name of the person you want to share with and select their Permissions for the shared folder.  Make sure that you have "Folder visible" checked at the bottom right.
6)    Click Apply, then click OK
7)    Perform steps 1 - 6 for the parent folders of the subfolder all the way down to your named mailbox (  You do not need to give permissions to any of these parent folders, just make sure that the "Folder visible" box is checked for them.
       Example: If the subfolder is in your Inbox folder, you will need to share the Inbox folder with "Folder visible" and also your named mailbox.

To view a shared folder:

1)    Click File
2)    Click Account Settings
3)    This should drop down and click Account Settings... under Account settings.
4)    Under Email, click your name in the box below, then click Change above the box
5)    Click More Settings... in the bottom right.
6)    Click the Advanced tab
7)    Click Add...
8)    Type in the name or email address of the person who is sharing the folder with you.  (John Doe or
9)    Click OK
10)  Click Apply, then OK
11)  You can close out of the Change Account and Account settings windows.
12)  The new mailbox should appear with the person's name that is sharing it with you in your folders on the left side of Outlook.