Most store-bough corned beef comes either pre-seasoned or with a tiny spice packet. If it comes pre-seasoned, you don’t need to add anything else to the water. If it comes with a spice packet, use the seasoning in the packet to either season the corned beef or sprinkle it into the cooking liquid. If your corned beef did not come with a spice packet, all you have to do is add some pickling spices which contain many of the same ingredients used to season corned beef.