How can I connect my circuit to power?

I am trying to build an escape room puzzle, where someone holds a key fob up to a sensor and a maglock opens, and I went online to buy something that I assumed was ready-in-box but instead they sent me the photo attached which I'm 99% sure was originally a car immobilizer and is now being used as a sensor with attached output. My questions is - how do I connect this to power? I have some knowledge in electrical engineering, enough to recognize most of the parts here but this is the one mystery I cannot solve. The whole thing I assume takes 12V power. Does anyone have an insight into how to give it power, or even how to set it up in general?
In photo: circuit board in the center, sensor (large, black) just off center right, attached chip up top/middle is output (for maglock), coiling wires off the right side is just a singular LED light, and included fobs are top-right. The rest is a mystery.

Hi,

At a guess, but don't take my word for any of it: The blue cube is a relay or a transformer? The connectors behind it are for you to connect phase and neutral or a DC input? The metal tab sticking out of the heatshrink (mmm, safe design if that's a "hot" tab) that comes from the relay/transformer board may be a power transistor or similar? Black wire is ground, red is VCC (12V?). I can't imagine what the white wire is for, it says "in" on the little relay/transformer board, and it's connected to the yellow wire too, maybe it's a MOSFET gate connection?

Notice all the question marks... I could be very wrong about everything.

Have a look at the other side of the blue cube, the PCB may have written what needs to be connected there in the screw terminal block (e.g. phase and neutral or another DC voltage), and read what it says on the top of the relay/transformer, from that info. you should be able to locate manufacturer and part to know what it is.