how do you use set velocity is there a tut or somthing that is 1 comand i have trouble with
It is a very simple command, but how you use it will depend entirely on the situation. It works like this:
vehicle setvelocity [x,y,z]
x is the amount of speed you will give the vehicle in the west (positive number for x) or east (negative number for x) direction. y is the amount of speed in the north (positive) or south (negative) direction. z is the amount of speed in the up (positive) or down (negative) direction. The speeds are all in meters/second.
A common use of the command would be to give an object a push in the direction it is facing. In this case, using our knowledge of basic trig, we use the command like this:
vehicle setvelocity [V*(cos getdir vehicle), V*(sin getdir vehicle), 0]
This will make the vehicle move at V m/s in the direction it is facing.