Go to Tools | E-mail accounts, select "View or change existing directories
or address books", and click OK. If you don't see the Outlook Address Book
in the Directories and Address Books list, click the Back button, then
select "Add a new directory or address book", then "Additional Address
Books", and add the OAB.  Then keep clicking Back until you get back to the
first dialog box, and go back to the Directories and Address Books list as
you did earlier. Once the OAB appears in the list, select it and then click
Change to make sure the Contacts folder(s) you want to display are listed.
If any of them aren't listed, you'll need to enable those Contacts folders
as Outlook Address Books by right clicking the folder, selecting Properties,
clicking the Outlook Address Book tab, and checking the "Show this folder as
an E-mail address book" box.  Make sure you restart Outlook after making
these changes.