After much trial and error with using various types of video editing software, we found that using your phone recorder to record your narrations works very well. Most phones format these clips in formats friendly to most video editing software. One suggestion you may consider is renaming your audio clip the using the slide number it is to be used for. When putting it all together, it will help you keep track of what should be paired.
Things to Consider
In addition to renaming each narration clip the same slide number it is to be paired with in the video editing software, you may also consider doing the following as well: