I have the Magix Movie Edit Pro software. I thought I could use it not only to edit clips of my movies, which has been easy, but also to replace the audio portions of my digital video recordings with music. Can you help?
You need to be working in 'timeline' mode where the objects (clips, images, sound files etc) are displayed on horizontal numbered tracks. At the left end are the track numbers and some other controls ('S' & 'M' etc) for each track.
To have music rather than original audio you do not have to delete the audio but can simply click on its 'M' to mute it. The music is added by dragging a sound file to any track below (higher number) your original clip.
If you don't first mute your audio you will get a mix of the two sounds. You can control the mix as well but that gets a bit beyond a quick reply. I Hope this gets you started.