At most of the airport car parks you'll get the option to select valet parking. When you select valet parking you'll hand over your car at the airport, and you don't have to drive to the car park itself.
On the day of departure you'll drive directly to the airport. Most of the time you'll need to contact the car park before your arrival at the airport so they can make sure that a driver is waiting for you at the airport. They will check your car for damages before you hand over your car keys. The driver will park your car at the car park, and you can check in for your flight.
On the day of arrival you will need to contact the car park after you've got your bagage. They will make sure that your car will be waiting for you at the airport when you come out. You'll get your keys back after an inspection of your car, and you can continue on your journey home.