If you have a Windows 10 computer it comes installed with a program simply called (Microsoft's) "Video Editor." Click on the Start button in the left corner of your screen and scroll down to the "V'"s. It should be listed there.
You can insert photos at the start or a title card if you want, then add videos, edit them down to the sections you want, or the length you want. Split them so you can edit some middle parts out, add more photos etc. There should be many tutorials on line on how to do it or some YouTube tutorials.
It may take you some time to figure it out the first time, so be patient and reserve some hours to learn it. I copy various art lessons online, especially live videos by fellow professional artists and then cut out all the extraneous talk and waving to people as they show up to watch, etc. I often cut an hour and a half live video down to the necessary 22 minutes or so of instruction and demos that I really want, from beginning to end. This is for my personal use only. This way it doesn't take up so many megabytes on my computer. It can take me now 20 minutes or so to edit it, and I know what I'm doing now.
Windows 8 computers and lower have something called "Movie Maker" which does about the same thing. Although, I don't know if photos can be added.
Mac computers have something similar installed.