It's not that difficult.
Please read what's on here:
http://www.nonumber.nl/contenttemplater
After install, just try to make a template in the Content Templater component and see what happens.
You can enter anything you want in the settings / content that you want the template to set after choosing it in an editor.
You can even leave the content empty and use the template to just set certain publishing settings or whatever.
Best way to see how it works is just play around with it. That counts for most extensions.
I am currently working on an import / export function. When that is finished, I can publish some example templates that you can import into Content Templater.