Click the Calendar Sharing Info button located to the right of the name of the calendar you'd like to add.
Ensure the Public Calendar box is checked. This will enable PrintableCal to access the calendar URL.
Click the Copy Link button located below the URL.
Click the OK button to close the Calendar Sharing settings.
After copying the link, the address field at the top of the Add Calendar Source - iCloud window should be automatically filled. If that doesn't happen, right-click the address field and select Paste from the popup menu, or press Ctrl+V.
Enter the name of your iCloud calendar in the field below the calendar address field.
The OK button will become enabled. Click the OK button to add your iCloud calendar to PrintableCal's list of available calendar sources.