2. Open Windows MovieMaker
3. Click on the 'Tools' Menu , then 'Narrate timeline'.
4. Check 'Front Microphone' from the Microphone drop down menu
5. Click 'Start Narration' and speak into your microphone.
6. When finished click 'Stop Narration'.
7. Press the play button to listen to your narration
Check out Adding A Narration to Your Movie for more help.