Simply connect the red wire to the positive supply, and black to negative ground. The display has a microcontroller that will read the voltage, compare it to a stable reference and display the voltage with 0.1V precision on a 3-digit 0.56″ tall 7-segment display. It works from 4.5V up to 30V and is reverse-polarity protected so it will be good for nearly any electronic project! The meter draws 3-4mA to power the microcontroller and display. This particular LED display is a nice vivid green, which we found very readable. To mount to your enclosure, simply cut a 45.5mm 26.5mm rectangle and snap it in.