How can I load cargo on the car

How can I load cargo on the car
as in the picture

 

There isn't really a way of spawning them like that, but you could use the node grabber to lift the cargo and put it where you want it, then attach it to the nodes of the vehicle to get it to stay in place. Doesn't always work but it's worth a shot.

 

You can attach cargo to the D and H series.

 

If you press ctrl you can drag nodes to do it that way.