The process is easy:

1) Take a ticket from the ticketing machine as you enter into the parking lot.

2) Take that ticket with you as you go into the airport to meet your party. (Don't leave it on the dash of the car, for you will need it for step 4.)

3) Find the parking kiosko (looks a lot like an ATM) which is located inside the building between Departure and Arrival.

4) Put the ticket in the machine, and the machine will prompt you for how much you owe. Pay that amount.

5) Take the ticket with you. You will use the ticket to raise the arm to let the car out of the parking area.

I can't remember what it costs. More than you'd think, but not enough to be significant. Maybe $5 for the first half hour and $3 thereafter, or something.