Measure the length of your picture. For optimal results, you want the middle of the image to hang at eye level. Eye level varies by height, but a good average is 57 to 60 inches. Pick your favorite and mark this off on the wall in pencil.
Hold the image so it's centered at eye level and make another mark at the top of the frame so you have a guideline.
Turn the picture over and look for a wire or hook on the back. Measure how far down this hangs from the top of the frame. A hook might hang 1 inch down, for example. In this case, make a third pencil mark 1 inch below the dot marking the top of the frame. This is where you want the picture hanger to go, so the image is centered at eye level.
Select the right picture hanger based on the weight of the image. Some support up to 30 lbs., while others hold more weight. Make an educated guess on how heavy the art is by how it feels to lift.
Slide the pin-head nail through the J-shaped picture hook. Hold the hook flush against the wall with the tail of the J lined up on your dot. The nail will be at an angle, which is fine.
Hammer the nail into the wall.
Hold the picture up to the wall, above the hook, then slide it down so the wire or hook catches the J and rests on the picture hanger. This can take a few tries to get right, so don't let go if the image until you feel it snag on the hook.
Push the image left or right to level it, checking the grade with a spirit level.