HOW To Add a Shared Calendar in Outlook
Go into your Calendars in Outlook.
On the left, right-click on MY CALENDARS.
Click Add Calendar > Open Shared Calendar.
A box will pop up. Start typing the name of the calendar you want to see.. Click OK. It will automatically open and appear on the left hand side of your calendars bar.
Whenever you want to show them, toggle them on/off as you need. You can also see the boardroom, chatrooms and vacation calendars this way.