From the Canberra Airport website:
DISABLED PARKING
A number of designated disabled car park spaces are conveniently located in the airport car parks. To access these parking spaces, enter the car park via the boom-gate and take a ticket from the machine as you would normally.
Upon leaving the terminal you will need to pay for parking at the pay machines before returning to your vehicle. Our pay machines have been specifically designed to enable people in wheelchairs to access them with ease. If you experience any difficulties with the ticket or pay machines, press the help button and a member of staff will come to your assistance.
[my emphasis]