what is an astern lamp or how to connect a parking sensor?

i just bought a parking sensor for my car. i have some knowledge but it said in the direction connect the mainframe power wires to both the negative and positive end of the astern lamp. the wires are thin and are pretty long and i can run it to the car battery it said i need a DC12V operating voltage. and a max power consumption of 4W. it is suppose to turn on auto when i go in reverse but i also don’t see anything that will tell it to work all it brought was the mainframe, detectors, the display, the buzzer, and all its wires can anyone help. to where i can connect it so that it works. or that it doesn’t drain my cars battery.
i did its only one page and im guesing about connecting it to the battery since i have about 15ft of wire

try to check it out first on auto repair shop..