Capturing your screen, your audio and your smiling face into one slick video is actually not difficult. There is commercial software that will do this; but for a basic video that just rolls through your PowerPoint slides as your smiling face talks in the corner, there are free solutions that work very well. One of them is a program called "OBS Studio" which works on Windows, Macs and Linux. It's widely used and there are lots of tutorials floating around on the Internet, both in the form of YouTube videos and PDF manuals, so you can pick the style of learning that's easiest for you.

You can download OBS Studio from https://www.obsproject.com. If you're not exactly sure how to download and install it, here's a YouTube video that starts by showing you exactly what you have to do: https://www.youtube.com/watch?v=ySENWFIkL7c. This same video goes on to give you an introduction to how to combine screen, audio and your webcam to show an inset of your face  in the corner. It's a perfectly good video, but the guy's voice is a bit irritating. Here's another tutorial by someone with a more pleasant voice: https://www.youtube.com/watch?v=-puA85ciDEM.

If you prefer to have it all in a single PDF file, there's one here, and you can use Google to find similar tutorial manuals in many other languages.

The nice thing about software like this is that you can do your presentation in any way that is comfortable to you: as a PowerPoint presentation, as a single-page giant PDF file that you pan-and-zoom around (if you prefer a poster-style talk), as a Prezi.com presentation ... lots of good choices. Software like this also makes it easy to assemble your presentation in segments and stitch everything together at the end, like a movie director.