Using Unused Pins of Motor Shield V1 to light LED

[oliviab]

I am trying to use an unused pin from my motor shield V1 to light an LED.

I understand that analog pins 0-5 are available. I am using analog pin A2.

To complete my circuit that I am building on a breadboard with a resistor and the LED, I need to connect to ground. How do I access ground on the shield? May I plug into the same ground as the blue external power? Or is there another ground I should connect to?

[adafruit_support_bill]

All grounds are connected to the same Arduino ground. Use whichever one is most convenient.