It's like all other ports, it's up to you to get from the airport to the port. The cruise line will offer, at a cost, transportation from the airport to the port. However, this transportation is only available the day of departure. There are many business providing alternative transportation oftens much cheaper and more flexible.
Many have found it attractive to rent a vehicle for transportation to and from the port/airport. This is especially attractive for arriving days prior to departure. We arrived the day early, rented a car in MCO, travelled to Port Canaveral, kept the car for overnight use, then left the car at the rental agency who provide free transportation to the port.