This article explains how to add public folder calendars to your Calendars tab in Outlook.
Prerequisite
You must have permission to access a public folder calendar before you can add it to your Outlook profile. To request this access, please contact the Help Desk to submit a ticket for you.
Adding the Calendar
To add the public folder calendar to your Outlook profile, please follow these steps:
1. Sign into Outlook online with your NKU account.
2. Right-click your email address above Inbox, and select Add public folder to Favorites:

3. Expand All Public Folders to see the list of all available public folders.
4. Expand the public folder related to your department or group, which should contain the calendar you want to add.
5. Click on the calendar, then select Add Public Folder at the top.

For More Information:
Please see this Microsoft article on adding public folders to your Outlook profile.