First, in case you don’t know, “Scratch” is a programming language and environment.
Its mascot is a cat, of course, but the name “scratch” supposedly comes from the use of scratching by disk jockeys. Scratch was first developed at MIT back in the early 2000s, and has advanced considerably since then. You now see the basic format of this language either duplicated or mimicked in many different environments.
Scratch can be an online langauge or you can run a stand alone version, but the former is easier and better. To get started, go here and follow instructions.
If you want (your kid or you) to learn scratch fast, you may want to consider getting the cards produced by No Starch Press. You can get ScratchJr Coding Cards for ages 5 and up
The idea is simple. You put the stack of cards on your desk next to the computer, which is tuned to the MIT Scratch site. Then you try out the stuff in the cards. By the time you are done you (or your kid if you step aside and allow access to the computer) will be pretty good at scratch programming.
By the way, Scratch runs on the web so you can access it from any sort of desktop or laptop computer including Chromebooks,a nd there are iOS and Android versions. It runs on the Kindle Fire as well.