How do you cook a pre cooked ham?

How long do I cook a precooked ham? It is 15 lbs. A precooked ham does not have to be cooked, but will taste better if you heat it thoroughly to an internal temperature of 140°F (60°C) or so. Place the ham in a 325°F oven (163°C). It will take 12 to 15 minutes per pound for a whole or boneless ham and 18 to 20 minutes per pound for a half ham.