Instructions
 
Tap the "Nintendo DSi Sound" icon, from the main menu of your Nintendo DSi, to launch the program. 
Tap "Record and Edit a Sound." 
Tap any of the white balloons. 
Tap "Record" and speak into the microphone, or play your sound into the mic to start auto-recording. 
Press the "Stop" button to stop recording. Sounds can only be 10 seconds in length. At 10 seconds, the recording will automatically stop. 
Tap "OK" to save your recording.