If you have not yet been given permission to use the shared calendar
Your supervisor will need to enter in a ticket to grant you access to the shared email. Once permissions have been granted you will then automatically have the shared email show up in your Outlook Desktop App and you will then be able to access it through the Outlook Web App as well.
How to access the shared email through the Outlook Desktop App.
Shared emails are always automatically added to your Outlook Desktop App once the permissions to the shared email have been granted to you. You may need to close out of Outlook and open it back up in order for it to update your Outlook and pull the new data. In some cases, there can be a delay until it finally shows up. We always recommend to give Outlook up to an hour to let everything sync up.
How to access the shared email through the Outlook Web App.
Please refer to this other article that covers accessing shared emails through the Outlook Web App:
Opening another mailbox in the Outlook Web App