This is a long video, however, it covers all the basics. Being a video, you can pause, go backwards, forwards or whereever!
This is the official Shotcut tutorial for adding a voice over. You can record your voice narration over video and pictures. Thanks to the Shotcut Tutorial Channel.
Another tutorial by Tux Designer showing you how to add a music track to your video - useful for background music.
You might like to have an animated introduction title at the start of your video. This short video from TuxDesigner shows you how to create one, as well as some other editing tips: