The mission starts with a cutscene. Once you’re in control, head upstairs and enter the room there. Grab the keys next to the dead body.
Go outside and get in the truck. The controls might feel a little different from the other games in the series, so you’ll have to get used to it at first. Head to your destination and avoid hitting cars and pedestrians as much as you can. Once you’re at the waypoint, drive the truck to the green marker in order to complete the mission.