How do I create a new trade??

Hello, amisare_bewaswerebeen,

In order to trade cards with someone on Deckbox you must first visit their profile (eg. http://deckbox.org/users/sebi ). On that page you will see next to that person's name, on the right, a button 'Trade' which should take you to the nice trade page where you can start selecting cards for the trade.

I hope that helps!