Swap it don't shop it. Swap ! Shop is a place for people to trade all of their stuff for new and different stuff! It's kind of like craigslist but less creepy. All you have to do is sign up and start adding listings. You can then entertain trade offers from other users or make offers yourself.
You can view all of the listings on the site to determine what items you want to trade for.
It's simple to add a listing. All of the swap options are on the left nav bar, to get started just select add a listing and you're off and running.
Once a listing is added you can view your listing and check to see if you have any offers.
Once you have an offer, you can view the offer and barter back and forth with the user who wants to trade for your item