there should be a prepaid return label...just put them back in the box they came in, slap that return label on, and you're all set. they have free returns, regardless of the reason.
Just login under your account on the website. Click on your order and follow the steps to return/exchange. It'll give you a prepaid shipping label, you'll need to print it out, tape it on the box, and hand it to the UPS guy! Hope this helps.