Here's an easy guide for getting audio into your Windows Movie Maker project.
Pasting Around Clips
Video editing requires you to combine all sorts of different media types together in a creative way so that you create a new entity entirely. This does not just mean a collage of video and still images, but a host of different types of outside audio. This material can be imported into your Windows Movie Maker project independently and does not have to be associated directly with a video clip. This is made incredibly easy in Windows Movie Maker, mainly because it treats these audio segments as just another piece of the puzzle.
There are a few different ways to import the special audio file you are looking for. If you go to the left hand Movie Tasks window you then go to the first option, which is Capture Video. Here you go and select the "Import audio or music" option, which then opens up a file finder window to search on your hard drive or devices currently attached to your computer. If you do it this way the only files that will be shown will be audio files that are supported by Windows Movie Maker. Another, and possibly easier, way to import audio is to simply go to File in the task bar and select Import Into Collections. Here you are presented with a search menu just as you were the other way, but now you have the option to import any type of media file and not just an audio one.
No matter which way you do this you then import the file into your Collections. From here you can drag and drop the file into the middle audio track of your Timeline. Since only one blank audio track is allowed in Windows Movie Maker you cannot put music and sound effects on separate tracks. If you want this you have to combine and export them in another audio editing program before importing them into Windows Movie Maker. Windows Movie Maker is dedicated toward simplicity in all areas instead of complex media development, so remember that if you want to have more advanced audio options you need to find a more advanced non-linear editing system.