1. With Outlook open, click the File tab.
  2. In the Info section, click the Account Settings button then choose Account Settings from the drop-down list.
  3. Double-click on your email address in the Name column. The Change Account dialog box opens.
  4. Click More Settings button from the bottom right. The Microsoft Exchange dialog box opens.
  5. Click the Advanced tab.
  6. Click Add button. The Add Mailbox dialog box opens.
  7. In the Add mailbox field type the email address of the mailbox you want to add and then click OK. The mailbox name should be added to the Open these additional mailboxes list.
  8. Click OK.
  9. On the Change Account dialog box click Next and then click Finish.

    A video guide on this is below.

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