Grab the string with a nice deep hook and pull straight back to anchor in one quick movement while at the same time pushing forward with the bow arm. Keep your elbow in line with the string or slightly higher but not that high elbow thing beginners are often taught. Try to hold the bow's weight at full draw using your back muscles which allows your forearm and hand muscles to stay nice and relaxed. If you can't hold at full anchor for 10 seconds you are probably overbowed. Pain is not good and is a signal that you are doing something wrong. That does not mean that archery is causing the pain - it could be that archery shows up a disfunction that is being caused by something else entirely - check out
www.egoscue.com The Egoscue Method keeps me functioning despite the abuse I give my body.