is this the same hood that came off? if so, check the underside of the hood, where the hinges bolt to it. there's probably a dirt/grease/paint fade line where the hinges used to be bolted. loosen the bolts and line the hinges back up with those marks. if there are no such lines, you'll have to tinker with it until you get the alignment right.
if this is a new hood, you'll need to mess with the hinge alignment as well as adjusting the two pads on the core support.