Ride a car into Marshall and look for Ray in an automotive building. He will give you a semi-broken sports car as a reward. Head into the marked location using the car he gave you. Avoid damaging the car at all costs since the mission will fail if the car blows up or even flips over.
Upon reaching the fields you will need to run over some zeds first as per request by Ray. Then head over to the marked area to end the mission.