"iCal" was the name of the calendar app/program used before Mountain Lion, now it's called Calendar.
Since "iCal" is the name of an app, I don't know what you mean by "add"ing it to icloud.
If you mean you want your calendars synced to other devices via icloud, then you need to go to the iCloud setting (on iOS look in Settings, and System Preferences on a mac) and turn on Calendar.
To add a new calendar to the set of calendars:
If on icloud.com with a browser, click the Calendars button in the upper left, click Edit, then the + button.
On a mac or device, look for the same kind of thing.
pvonk, you've confused the Internet Calendar standard with an Apple product. iCal is a standard format for calendar information: http://en.wikipedia.org/wiki/ICalendar
I have the same question, how do you add an iCal feed to iCloud?