Most crab legs sold today, are pre cooked and only need reheating. If your legs are bright orange, they are pre cooked, if they are greenish brown, they are raw and need a longer period of cooking.
In a large kettle place a couple of cups of water and bring water to a boil.
Place crab legs in pot and boil with lid on for 3-5 Min's if the legs were pre cooked.
If the legs were raw, continue cooking for about 10-12 minutes. until a bright orange color.