Either get a cheap set of open-ended wrenches (usually a lot thinner to fit between the crank arm and pedal), or simply take it to a bike shop to get them to loosen it for you--they shouldn't charge you for that. When you're standing over the bike like you are going to ride it, the right one can be loosened with "righty-tighty, lefty-loosey"... meaning counter-clockwise. However, the other pedal is reverse threaded to keep it from coming loose as you ride. Turn this one clockwise to remove it. It also helps to put a little spot of grease on the threads (not a lot) to make it slide in easier and make removal easier if you think you might change pedals again anytime in the bike's future.