This script DOES NOT spawn the vehicles itself. It merely provides functionality to the trucks to use them as mobile shops. You will need to find your own way to spawn the vehicles. Below are some ideas on how you could do this
Liveries
In case you haven't figured it out by now, you need the proper livery to actually use the truck. However you choose to spawn the vehicles make sure you have the vehicle spawn in with the correct livery. Default livery for both trucks is 1
Ideas on how to spawn
Using a Job Garage script
Write custom logic to spawn the vehicle and use the SetVehicleLivery
vMenu
There's plenty of options to choose from, but the above are the most common
