1. Sign into your account on Outlook Web App (OWA).
2. Click on the profile picture in the top right-hand corner and select Open another mailbox....
3. When the Open another mailbox window appears enter the name or email address of the shared mailbox and click on Search contacts and directory.
4. When the confirmation of the shared mailbox appears, click Open.
The shared mailbox will now open in a new tab.
1. Sign into your account via OWA.
2. From the left navigation panel click Folders > More and right click on your name.
3. Select Add shared folder...
4. Type the shared mailbox name or email address and select Add.
You should now be able to view the shared mailbox on the left-hand side of the navigation panel.