To trade via Wi-Fi, go to any Pokemon Center and head downstairs. Just talk to one of the receptionists, and she will lead you inside, and you'll connect to Wi-Fi. Then, if you registered the other person's Friend Code, and that person registered yours, that person should appear in the room with you. After that, one person can select what you two are going to do. Accept the trade offer, and that's all there is to it. Hope this helps. I'm bad at explaining things, lol. And about that trade... my Elekid for your Riolu?