Follow these steps to add events from an external .ics calendar.
In the left column, near the top, click the Calendar link.
Decide on the calendar where you want to import, click the arrow to its right, click Import External Calendar.
Enter the URL of the calendar you wish to import.
Click the blue Import Calendar URL button.
TIP: If you are importing a Google Calendar URL, you want to copy the link that says, "Public address in iCal format."