Hello,
I connected mine to the hot lead on the starter solenoid and ground.
It is running whenever the battery switch is turned on.
Not completely accurate but considered it close enough.
I used purple wire in the console which is the coil and when the motor is started power is applied to new hours gauge works like a charm. I will get pictures and post shortly.
I used purple wire which I'm told is a coil wire so when the start switch is turned to the on position power is given to the hour's meter and it starts tracking the hours run. see a pic of what my hour's meter looks like to the left DC volts are also shown on the gauge.