Summarize the following:
Wire plate hangers come in different sizes, so you need to know the size of the plate before you can purchase the hangers. Use a ruler or tape measure to determine the vertical length of your plate.  If you have a simple circular plate, you only need to know the diameter. Similarly, if you have a perfectly square plate, you only need to know the length of one side. If you have a plate with uneven sides, like an oval or a rectangle, first determine which side will be the vertical side when you hang it. Measure the length of that side and choose your hangers based on that. You should be able to buy a standard wire plate hanger at most hardware stores and craft stores. Look for the size that best fits the dimensions of your plate. Usually, the different size ranges are:  5 to 7 inches (13 to 18 cm) 8 to 10 inches (20 to 25 cm) 10 to 14 inches (25 to 35 cm), holding up to 30 lbs (13.6 kg) 14 to 20 inches (35 to 51 cm) There should be two wired ends attached by a long spring. The single wire piece with the pointed center should be hooked over the front top of the plate from the back, and the two-wire end should be hooked over the front bottom of the plate from the back.  Note that the spring connecting both ends should be hidden behind the plate. Due to the placement of the spring, the plate will stick out from the wall a bit. Take that into consideration when using these hangers. These hangers work best with plates that are fairly normal in shape and size. If you have to distort the springs too much to make the wires fit, the plate will be unstable and more likely to fall off the wall. Decide where you want the plate to be on the wall and mark the spot with a pencil. Hammer a nail into that spot. At least half of the nail should be inside the wall, but you should also make sure that there is plenty of nail space for the hanger to rest on. To determine where you want the plate, hold it up against the wall and move it around until you find the right spot. Lightly mark the top of the plate with a pencil.  Set the plate down, then measure the distance between the top of the plate and the pointed top of the hook. Make another mark on the wall the same distance away from your original mark. The nail should be hammered into this second mark. Carefully hang the pointed end of the top hanger onto the nail on your wall. This should complete the process.  Check the plate after you hang it. If it is not evenly aligned, you may need to readjust the positioning of your hangers on the plate. If the plate does not seem secure, change the position of the hanger or nail until it does. Alternatively, try a different hanging method.

Summary:
Measure the plate. Buy a wire hanger. Attach the hanger to the plate. Hammer a nail into the wall. Hang the plate.