Instructions
Turn on the Nintendo DSi and tap the wrench icon in the menu page that opens. Tap the "Internet" button in the menu that appears.
Tap the "Connection Settings" button and press "Advanced Setup." Tap one of the open profiles and tap the "Wi-Fi Protected Setup" icon.
Tap the "Push Button Connection" button on the DSi and press the "WPS" button on your router until the "Wireless Indicator" LED on the DSi lights up.