1) If you use Google Calendar: From the calendar image above click on "Add to Google Calendar" (or "+" if on a mobile device), OR
2) For all mobile device calendar apps: Open your preferred calendar app, go to your Calendars section, click on "Add Subscription Calendar" and copy/paste this url: https://calendar.google.com/calendar/ical/27ebda6d907240f1025783e5f7b0b2bc57ea173c666047d82598344d9a3a4839%40group.calendar.google.com/public/basic.ics