Instructions
Open the cover for the SD card slot, located on the right-hand side of the DSi. The cover does not come out completely, and you must not twist it or pull it too forcefully. Doing this may warp it and make it impossible to close.
Slide the SD card into the slot so the label faces down and the flat side points outward. You will know the card is inserted fully when you feel slight, springy resistance and hear a soft clicking sound.
Push the cover back over the slot gently.
Turn on your DSi and locate the application you want to use. For example, tap "Camera" to open the application. Tap "SD Card" to switch to that memory format, and then click "Album" to view the photos stored on your card.
Tap the SD card symbol on the DSi dashboard. This lets you view applications stored on your card, such as downloaded DSiWare games and programs.