Bulgur has already been cooked once (by the processor). You are, effectively, just rehydrating it. All bulgur is a little bit different, so it pays to check the packaging for any specific instructions. That said, if you have only a jar of bulgur and no cooking instructions, please know you have three options. One, boil in salted water until tender and drain (remembering that it will go super quickly because it has been parcooked). Two, boil an equal amount of water to bulgur by volume. Pour the water over the bulgur and let soak until tender, about 20 minutes. Three, soak the bulgur in an equal part of cold water overnight.