Everything is explained in the
Official Scripting Documentation.
There's a section for making your first script, it's very easy to do.
I agree, I wish there was a video, but if you think about it, all the different computer languages: HTML, PHP, C++, etc. are best taught by reading it yourself. It just wouldn't be possible to teach in a video. I wish it was, but unfortunately it's the same for learning to script, if you want to learn, you've got to make the effort to read the book and learn it
.