Note: You must have "full access" AND "Send As" privileges on the shared mailbox granted from the Outlook Administrator in order to perform these steps.
1.Login to OWA.
2. In the upper right hand corner, click on your account name and type in the name of the shared mailbox you want to access and click "Open".
Figure 1: Name dropdown and mailbox field
3. Click on the Calendar navigation button on the left.
4. Check the box next to the calendar you would like to share with another user.
5. Click the "Share" button on the toolbar and click "Share This Calendar…"
Figure 2: Share menu.
6. Address the invitation to the user you want to have access and select permission option (add, edit, delete). Click "Send."
7. The user will receive an email in their inbox with the option to "View This Calendar." Once they click it, it will appear in their calendar navigation.