Hi,
Welcome to PlayMaker!
This script is a special script, it's not something you drag directly onto the GameObject, but rather drag inside your Project folder, and PlayMaker will recognized it as an Action you can use like any other, and so once you have this script inside your project folder, it will be listed in the Action Browser, and you can drag it from the Action browser into a Fsm State.
Does that make more sense?
Also, I strongly recommend you use the
Ecosystem browser, it's meant to solve the issue you are having. This script is actually registered within a system that let you search for custom actions, samples, and packages for PlayMaker, and in one click it gets downloaded and installed for you, ready to be used within your project.
Let me know if you still struggle with this.
Bye,
Jean