If you are given access to an additional mailbox, you can add it to your Outlook client:
Go to Tools>Accounts
Click on ‘Advanced’:
Click ‘Delegates’:
Click the ‘+’ sign beneath ‘Open these additional mailboxes’:
Type the name of the additional mailbox, highlight the correct mailbox and click ‘Add’:
Confirm that your mailbox has been added, click ‘OK’:
You will see the mailbox added below your other mailbox accounts. It may take a few minutes to popup.