Most galleries hang their oil paintings at average eye level, about 58 inches high. The center of the artwork, not the top of the piece, should be at that height. This means you need to do some math: Measure the distance between the wire and the top of the frame, and measure the height of the art and divide it in half. Measure 58 inches on the wall, add the measurement of half the art's height and subtract the distance between the wire and the top of the frame. Put the nail here.