Instructions
Select "Settings," represented by a wrench icon, from the Nintendo DSi main menu.
Click the "Right Arrow" twice to reach the third page of options. Select "Parental Controls."
Choose "Yes" and then hit "Next."
Click "OK" to reach the PIN screen. Tap "Next" and enter a four-digit PIN using the on-screen keyboard.
Click "OK" to save the PIN. Enter the PIN again when prompted, and tap "OK."
Select a secret question and then select "OK."
Enter the answer to the secret question using the on-screen keyboard. Click "OK."
Tap the left and right arrows to select a gaming rating for the highest rating that is suitable for viewing on the system. The lowest rating is "EC," or "Early childhood," and the most mature rating is "AO," or "Adults only." There is also "RP" which stands for "Rating pending." To lock the DSi, select the lowest rating that will prevent anyone from playing any game on the device.
Answer "Yes" or "No" to lock PictoChat, DS Download Play, the DSi Browser, Nintendo DSi Points, the ability to exchange photos with other DSi owners wirelessly, and user-created content. Select "Yes" to save the settings.