The shaft has a magnet on it, Depending on how far in or out the shaft is, the sensor on top of the vts will know where that magnet is.
Thats the only thing that drives the gauge.
Plug it in and put the key in, After the gauges light up you can move the shaft in and out and you will see the gauge move up and down.
No calibration to it. Its kind of a dumb system, It doesn't care what the motor is doing, It only cares where that magnet is located.
You should see if the gauge and sensors work. Just move the shaft slowly or rotate the worm gear a bit at a time and you'll see the gauge move as you do it.