Office 365 (Outlook 2016) - Subscribe to a Calendar
Follow these steps to subscribe to an internet calendar (also known as an iCal or .ics file) and have it appear with all of your other calendars in Outlook 2016. Before you begin, you will need the URL for the iCal you wish to subscribe to.
1. In Outlook 2016, click Calendar in the bottom-left corner of the window (if necessary).
2. Right-click My Calendars (or any other calendar group's heading) on the left-hand side of the screen to display the options for that group.
3. Hover over Add Calendar and select From Internet... in the sub-menu.
4. Type (or paste) the URL for the internet calendar in the "New Internet Calendar Subscription" window that appears and click OK.
5. Click Yes to subscribe to this internet calendar and add it to your list of calendars.
The internet calendar now appears in your list of calendars within the selected calendar group. In general, you will only be able to rename, move, and change the color of internet calendars you've subscribed to in Outlook 2013 because they are often managed by someone outside our organization.