Office 365, Outlook for Windows & Mac, Open Shared Calendar
Windows
In Outlook -> Calendars -> Home tab, choose "Add Calendar +", and click "Open Shared Calendar..."
In the Search box, look up a person's name, NetID, or calendar name and click "OK"
If there are multiple options, select the calendar you want to open and click the "Open" button
The calendar will open and now be listed on the left-hand column and can be toggled on and off with a checkbox
Mac
Note: This function is in a different location in the "New Look" for Outlook for Mac. You can find the adding Shared Calendars section under File -> Open -> Shared Calendar
For the "Legacy/Old Look" follow the steps below:
In Outlook -> Calendars -> Home tab, choose "Open Shared Calendar"
In the Search box, look up a person's name, NetID, or calendar name
If there are multiple options, select the calendar you want to open and click the "Open" button
The calendar will open and now be listed on the left-hand column and can be toggled on and off with a checkbox