OUTLOOK : MAC - Add a shared mailbox

To add a shared mailbox in Outlook for Mac, follow these steps:

Open Outlook for Mac.
Go to the Tools menu and select Accounts.
In the Accounts window, select your Exchange account.
Click on Delegation and Sharing.
Switch to the Shared With Me tab.
Click the + button at the bottom left.
Search for the shared mailbox you want to add.
Select the mailbox from the list and click Add.

The shared mailbox should now appear in your folder list under your main mailbox