MCU Electronic Power Switch
There are various places. 


if the source can supply the required voltage and current, you could place it between 'high to run' and ground.


The next step is 'after' Q2, but that has a switch in parellel, so your light will light up if that is pressed too. You could extend the circuit with a resistor or a few diodes to prevent this.


Q2 switches on when 'high to run' is high, so you could place the light between Q2's collector and V_battery.


Next is between the collector of Q1 and ground. Like the collector of Q1, it is also activated when the switch is pressed (and prevent this parallel activation is a bit more involved), so maybe that is not what you want.

One additional note: if you use a LED on any of those places, don't forget the series resistor.