From the left sidebar click the Plus icon to the right of the input labelled 'Add a colleague's calendar'
Click 'From URL'
Paste the above URL then select Add Calendar
iCloud Calendar
Open iCloud Calendar
In Calendar, choose File > New Calendar Subscription
Enter the calendar’s web address, then click Subscribe.
Enter a name for the calendar and choose a color to help you identify it on your calendar.
Choose iCloud from the Location menu, then click OK.
Outlook Calendar
Open Outlook calendar
Click on the Subscribe: iCal link below the header date on your Calendar (or select Open Calendar -> From Internet on newer versions) and Copy the iCal url.
Paste the link into the New Internet Calendar field then click OK.
Click [Yes] to the dialog box that comes up verifying you want to subscribe to it.