1. ​If you are a GOOGLE CALENDAR USER… At the bottom of the calendar there is a plus sign. If you click on it, it will ask if you want to import this google calendar. If you are logged into gmail at that time, it will import automatically.  Note that means that whichever gmail account you are logged in to at that time will then intercept the calendar.
2. IF YOU ARE AN ICAL USER:  From ical, go to File/New Calendar Subscription. Copy and Paste the URL below into the box. It will let you choose what you want to name that calendar and what color you want it to appear.  https://calendar.google.com/calendar/ical/mcpsmd.net_b55jc4kndh53hj16ik3ugt0v5o%40group.calendar.google.com/public/basic.ics