Add a shared mailbox using the Outlook desktop app for Windows

To add a shared mailbox, you need to make sure you have been given permission to it, as well as to any of its folders/subfolders.

1. Choose File | Account Settings | Account Settings
2. Select your Office 365 account and click the Change button.
3. Click the More Settings button.
4. Click the Advanced button.
5. Click on the Add button and type the person's name in the window (e.g., Jane Doe), and click the OK button.
6. Click the OK button.
7. Click the Next button.
8. Click the Finish button.
9. Restart Outlook.

The shared mailbox displays under your primary mailbox. You can expand or collapse the shared mailbox folders as you can with your primary mailbox. You also can remove the shared mailbox from your Folder list. To remove it, right-click the shared mailbox, and then click Remove shared folder.

If you need to be provided "Delegate Access", refer to "Assign delegate access using the Outlook desktop app for Windows"