Hi @Cat Miller
You can record your computer's screen while you are running the powerpoint slideshow. There are many screen recorders available in the market- OBS stduio (free to use), Screencast-o-matic.com, Camtasia etc.
You can record voice-over along with it or separately; and then merge/sync audio and video with each other. Once done, you can upload the final product - the video - in you course.
Hope this helps!