So... you bought a dsi and a sd card for it. You want to get music on it but you don't know how. Then this is the instructable for you! This insructable was made on a microsoft laptop, not a mac.
Step 1: Items
things you need
a sd card
an adapter for the sd card
a song you want to put on the dsi that is on itunes
Step 2: Converting
so right click on your song. Then left click on convert song to AAC. The dsi uses an AAC player. It will start converting. Wait for it to finish
now plug in your sd card. a window will show options to open the files on the sd card. choose open folder to view files. open up the file MISC. now go to itunes and copy the AAC version of the song.now go to the file MISC and paste the AAC music file
Step 4: Finish up
now put your sd card in the dsi. go to sound on the menu. choose play with your music. now you can choose auto or go to MISC and choose a song. auto chooses you a random song from the MISC file.
have fun with your music.