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.

You should also let it rest for 20 minutes or so out of the oven before you serve it.