Once the narration recording is saved, the narration clip is added to the Collections window at the top of the screen. Notice that the icon is an audio type.
Test your narration in the movie, by clicking on the Play button. If you do not like the results, simply delete the narration in the Timeline and record again.
Next Tutorial in this Windows Movie Maker Series - Video Transitions and Video Effects in Windows Movie Maker
Complete 7 Part Tutorial Series for Beginners - Getting Started in Windows Movie Maker