Log into your OWA at https://outlook.office.com
From the top-left hand corner, click on the app launcher (the nine little squares) and choose "Calendar"
On the left hand side, right click or press the control key and click on "Other Calendars" and choose "Open calendar"
Enter the name or address of the shared calendar you'd like to open and hit enter to search for it.
Click on the name of the desired person/calendar and click Open
Enjoy your shared calendars that show up under "Other calendars."
