Open the other calendars panel, click '+' and choose "From URL".
Paste your calendar URL in the text field and hit "Add Calendar" ( https://ics.calendarlabs.com/353/e2d8f20f/British_Virgin_Islands_Holidays.ics
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Your are now subscribed to the calendar. It may takes a few minutes for the events to show up.
Your Calendar is Ready
(Click "Add to calendar" to subscribe)
Automatic subscription works, when the 'Calendar' application is your default calendar.