As the other posters mentioned, you would contact your airline and let them know that you need wheelchair assistance at your departure and destination.
Usually, the flight attendant will verify with you during the flight that you need a wheelchair when you arrive. Flight attendants will also communicate with the gate agent at the arrival gate to make sure it is there waiting for you.
The skycap will push the wheelchair wherever you need to go - this includes places like baggage claim, car rental, the Disney's Magicl Express area - even drive you to a bathroom and wait or you outside.
Depending on the airport, they may have push wheelchairs or an electric cart - sort of like a golf cart.
Thank you for mentioning you did not find this information - I do have air travel information in the last post of page 1 of the disABILITIES FAQs thread, but that is one piece I missed. I
I will add it.