How do I view other users' mailbox in Outlook

from http://kb.iu.edu/data/agny.html we read:

If you have permission to access any folders in another user's Exchange mailbox in Outlook, you may open the folders on demand. If you need more frequent access to them, or access to a subfolder, you may add another user's mailbox to your Outlook Folder List.

Opening another user's folder on demand in Outlook 2000, 2002, 2003, or 2007

This method will allow you to open one of the primary mailbox folders (Calendar, Contacts, Inbox, Journal, Notes, or Tasks) in a separate window that will not reappear the next time you start Outlook:
1. From the File menu, select Open, and then Other User's Folder... .
2. In the Open Other User's Folder window, type the other person's username, or use the Name... button to select the person's name from the Address Book.
Note: You can only open the mailbox of another Exchange user.
3. From the drop-down list, select the folder you wish to open. If that folder is not listed, the only way you can access it is to add the other user's mailbox to your Outlook Folder List.
4. Click OK or Open. The folder should open in a new window. If you receive an error message about permissions, check with the mailbox's owner to ensure that you have permission to access the folder you're trying to open.

Adding another user's mailbox to your Outlook Folder List in Outlook 2000, 2002, 2003, or 2007

Note: Although you can add other users' mailboxes to your Outlook Folder List without having any permissions for their mailboxes, you will not be able to view them unless you have at least Reviewer permission.
1. In Outlook 2007, from the Tools menu, select Account Settings... . Highlight Microsoft Exchange, and click Change. Then click the More Settings... button.
In Outlook 2002 and 2003, from the Tools menu, select E-mail Accounts... and then select the radio button next to View or change existing email accounts. Click Next. At the next screen, highlight Microsoft Exchange Server, and click Change. Then click More Settings.
In Outlook 2000, from the Tools menu, select Services... . Highlight Microsoft Exchange Server and click Properties.
2. Click the Advanced tab, and then click the Add... button. This allows you to add mailboxes to your Outlook Folder List.
3. In the "Add Mailbox" field, enter the username or name (in lastname, firstname format) of the person to whose mailbox you have shared access.
4. You should now see the additional mailbox on the Folder List. (If you can't see the Folder List, select View, and then Folder List.) Any folders that a user gives you permission to access should be listed under the other person's mailbox. If you cannot expand the Folder List, the other person has not given you permission to access the mailbox.
5. If you like, you can create a shortcut to a folder by dragging it to the Outlook Bar (the leftmost column visible)