You taxi onto the re-arm pad and come to a complete stop. Your plane will be re-armed and re-fueled. It will go to the same weapons and fuel you selected when you first launched. It will not repair any damage.
I find this to be good practice in the offline practice arena. When you run out of bullets shooting at drones, land the plane, re-arm on the re-arm pad, and take off manually. This will teach you a lot about how to get your plane to do what you want it to do.