Verified answer

I think you hace to have a game with wi-fi like mario kart, go to the wifi option inside that game, look for connection or something, and i think your internet has to be open, not locked, I got rid of my ds like a year ago thoough so I might be wrong

you basically need to have a game thats able to play games through wifi. select this option in the game menu. there's also a secret way but cant remember it...