@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:
https://github.com/julianlam/nodebb-plugin-google-analytics/blob/master/lib/client.js#L9
