To set up or sync a shared mailbox in Outlook, you must first:

1. Ensure you have been given the correct permissions to access the shared mailbox.


2. Verify you are using an Office 365 subscription, the Outlook desktop program and an Exchange Online account.


3. Sign in to Outlook with your own account credentials.


4. Open the account settings option and select the 'Accounts' tab in the navigation pane.


5. Under 'Accounts' click on 'Add a shared mailbox'.


6. Enter the shared mailbox address and click 'Add'.


7. Open the 'More Settings' option.


8. Go to the 'Advanced' tab on the Outlook Settings window.


9. Check 'Download shared folders' and click 'OK'.


10. Restart Outlook.