Westfalia kitchen galley battery indicator switch

[candyman]

Hey all,
Sorry if this is a stupid question but electrical is not my strength and I want to make sure I do this right. So I purchased a cheapy led voltmeter indicator for my secondary battery. I basically bought one similar to this but not this exact one.

http://www.powerwerx.com/batteries-chargers/powerw...aQodefUPZQ

My galley switch is wired to my second battery already. But what I want to do is wire my led Voltmeter to the little toggle switch on the galley faceplate. Reason being is the led light is bright and at night I would like to option to switch it off inconjuction witht the stock indicator lights for fridge, battery and water tank level. So how would I proceed to wire this very simple device? Do I just join the two hot wires (new led and toggle switch) and then find a ground for the led ground wire?
Thanks in advance
Jason