Take the A57 westbound towards the airport. You can get to the A57 via the A26 if you're coming from the north or the south. When you get to the airport, follow the signs for the Long Stay car park.
If you're coming from Crumlin, take the A52 Mill Road out of the village. Mill Road will become Nutts Corner Road. At the first roundabout, take the first exit onto Tully Road. At the second roundabout, take the first exit onto the A57 Ballyrobin Road towards the airport.
If you're using a sat nav, the airport's postcode is BT29 4AB.