first whats the difference between an odf and msh

and second how do you add vehicles i dont understand how vehicle spawn or nothing works

It's all in the documentation. Read it, and if you don't understand it, read it again. It's relatively straight-forward.

ODF stands for Object Definition File. Basically it tells the object what it is i.e. a prop, weapon, or character. A MSH file is the object itself; don't mess with it.