There is a central area for guest drop off under the rotunda of the main parking structure. Take the escalator up and make a left through bag check. You are only about a five minute walk to the gates at IOA. There is no parking fee for guest drop off or pick up.
Follow the signs for guest parking and, as you round the corner, stay to the right. Tell the kiosk attendant that you are dropping off and they will direct you round tothe drop-off area on the other side. As Metro says, from there you go up the escalator and turn left through bag check and into City Walk