Thanks for the reply.
I had misunderstanding how this plugin works, now I got it.
It works now 🙂
Just for other users if they see this topic in the future: You should go to each Category you created before or create after that, click on Subscribe green button and the plugin should work for you like me.
For example in my website I have 3 categories called Q/A, Free Discussion and Announcements. I should subscribe in all these three and then just wait for another user to create topic.
@exobucks Best bet is to integrate the js code in your plugin itself, so all admins have to do is enable your plugin and that's that.
In your plugin you can execute your code in a client-side js file, and read the value of a configured ID from the plugin settings (if needed). You can see how this is done by inspecting how the Google Analytics plugin handles it: