In iCal, you do this by selecting "Preferences", selecting the Account pane, then hitting the "+" sign in the lower left-hand corner of the pane. In BusyCal, use the Calendar menu and select "Connect to iCloud/CalDAV server".
Changed:
< <
The account type is "!CalDAV".
> >
The account type is "CalDAV".
For account and password, use your standard Nevis account/mail password.