I just did this this weekend, so let me try to help you out.
Basically, the resonator routes the air coming into the stock airtake so it's quieter. It you add a Short Ram Intake, you don't need it. If you add a Cold Air intake, you HAVE to remove it so ithe new intake will fit.
It's a big white box that sits behind the passenger side headlights. You can get to it by taking of the bumper, but an easier way is to remove the passenger side tire and unscrew then peel back the plastic wheel well cover. There are 2 10mm bolts that hold it in (and a third on one of the 2 pipes that lead from it), undo them, give it a little tug and some shimmy-shammy, and you'll be able to wiggle it out.