Things You'll Need
Instructions
Find compatible audio tracks on your computer. The Nintendo DSi is only compatible with AAC audio files so you may need to find a program that converts music files into this format. There are many open-source programs that allow AAC conversion and some media players, such as iTunes, can also do this conversion.
Insert an SD card into the SD slot of your computer, or use a USB card reader if necessary. The drive will open on the desktop automatically. Create a playlist by dragging and dropping AAC audio files from your computer into the SD card. Make sure that the SD card is 2GB or under as the Nintendo DSi is not compatible with anything higher.
Remove the SD card from the computer and insert it into the DSi's SD slot. Press the power button on the console and select the Nintendo DSi "Sound" icon. Choose "Play With Your Music" and search for the SD card folder. Highlight the song you want to play and select "Start" and your AAC file will play through the DSi's speakers.