To modify a resource calendar, use the cscal utility modify command (csresource does not have a modify command).
For example, to set the owner as tchang and add another owner named mwong to the resource calendar named Auditorium:
cscal -o tchang -y mwong modify aud100
In this example, the cscal utility requires the calid (aud100) rather than the calendar name (Auditorium).