If you're okay with a paid solution Camtasia is probably the gold standard for tutorial/instructional videos, especially screencasts.
https://www.techsmith.com/video-editor.html
For something free, I've had success with OpenShot and used it for show & tells at work on a work machine that I didn't have a licence to use anything more 'professional' with but be prepared to finnick about with it, but for your simple use case it should do the trick. You can use OBS (https://obsproject.com/) or ShareX (https://getsharex.com/) as free tools to capture the screen and/or your webcam.