Here is my first try using Screencast-O-Matic. It is a video showing how to add an image to a DotNetNuke page.
The audio syncs with the video, but for some reason I lost the pointer tool. The video is not as large as I had expected, so it is hard to see details on the page. Quick Tips for Improving Screencasts mentions greater success when using a smaller screen setting than I used and an "autopan" feature that automatically moves the region being recorded as you move the mouse, which wasn't available in the software I used. Will try another software next time. I rambled shamelessly at the end of this video, cut to other pages thinking the video had ended, and then couldn't get the editing tool to work, so I can see that lots of practice is needed before creating a final product!
Decided to try another software, this time Camtasia. Much easier to use and more options for editing. And the pointer tool showed up this time! I still don't like the small screen size...