It isn't as simple as asking how to create a truck. You need to be able to build all the components. If you want a custom truck, you need to make the body for it, then the chassis, paint it, put all the components into it, and get it placed in-game. If you want to mix n' match truck parts, an example being putting the Ford F-150 body on a CRD with a custom paint, you would have to go through almost the same steps. You need knowledge of all the programs needed, and you need to somewhat know your way around Rigs Of Rods to start with.