Instructions
Connect the micro end of the USB cable into the Nintendo DSi; connect the other end into the PC.
Turn on the DSi.
Start MediaMonkey on the PC.
Look for the DSi as a storage device in the MediaMonkey library pane in the upper left corner. Alternatively, you can click on "Tools," "Options" and "Portable/Audio Devices" to find the DSi.
Select a playlist, auto playlist or manually select song tracks and drag them to the DSi icon in the library pane in MediaMonkey.