Installing DC/AC converter

I recently bought a new car and I am transferring my Monster Power DC/AC converter. It was professionally installed so I have never done it on my own. I successfully removed it from my old vehicle and almost have it complete, but there are 3 wires, one obviosly power, hard wired to the battery, one ground, and then this other blue wire. On my old car it was wired to a wire underneath the steering wheel, but I have no idea where to wire it to on my new car. HELP!

probably an ignition turn on alot like what audio amps use.
Simple fix is to use a manual swtich and just sent it a 12v + feed fused to <1a