So if you haven't used these before, put your item in the the shopping cart, go through the checkout process until there is a spot to put in a code (sometimes you can put one in right in the cart), then make sure you "update" so that the price is updated. DON'T checkout until the price is correct. Make sure before the FINAL checkout that the price has STAYED at the reduced rate!
You should be able to get about 10% off and free shipping! If not I'd call them.