You basically just add in and a time at the end to the shifts code. So once you have it set into the scene, whenever you want it to then move, you would use the shifts code with a number of seconds at the end of it. For an example, say this is the scene:
INT. BACKGROUND
&zoom reset
&cut to zone 1
&overlay CAR create
&overlay CAR opacity 1 in 0
&overlay CAR shifts to 0 0 in zone 1
&overlay CAR scales to 1.000 1.000
&overlay CAR moves to layer 4
^That’s the car set into the scene, with the shifts, scales and etc…
Then whenever you want it to move somewhere, say zone 2 or even across the screen, you would use show helpers, spot directing, change overlay, then drag it wherever you want it to go and copy that “shifts” code and then add it to your script but also add “in” and “a number of seconds” you want it to take to get there at the end of that code. Like this:
@overlay CAR shifts to 47 128 in zone 2 in 5
OR
&overlay CAR shifts to 47 128 in zone 2 in 5
you would place that code after your car is already set into the scene. And you can have it be in whatever number of seconds that’s just an example 
You would only need the scales code again if your car was changing size such as driving off into the distance getting smaller then you would also want to copy the scales code and add an “in #” at the end matching to the shifts code but if the size doesn’t change you don’t need that copy that again.
Also I would highly recommend checking this out:
She tells you all you need to know regarding overlays.