In the upper right corner of the screen, you should see a profile icon. Click it and select "Open another mailbox." In the search bar, type the specific email account and select Open.
Your browser will open a new tab displaying the email account contents of this shared mailbox.
Within the Outlook application (Win / Mac), select Calendar from the panel on the left and select the specific mailbox calendar you would like to view. Calendar contents should display within a few minutes.
With Outlook online (Win / Mac), click the small squares icon on the top left corner of the window and select Calendar. Calendar contents should display immediately.