Click on "Calendar" → "Add account..."
Choose "Other CalDAV Account" and continue
Choose "Advanced" account type, enter user name and password
Enter the server host name in "Server Address" (the first part of the URL copied from "CaldDAV URL Display" portlet).
Enter the path in server path (the last part of the URL copied from "CaldDAV URL Display" portlet).
Enter also the port number (usually 80 for http and 443 for https); if necessary check "Use SSL" and sign in.
Select in the "Calendars pane" which calendars you want to see.