For the future see this post for the best way to post flows - How to share code or flow json
The code passes a url to the the iframe, which loads the appropriate grafana dashboard. You will have to configure grafana with a dashboard showing what you want and then use the url of that dashboard in node-red. You can get the url from the browser address bar once you have it working in grafana. Forget about node-red for the moment, connect the browser directly to grafana and build the dashboard you want. That is where you will use the query I posted.
If you don't know how to configure a dashboard in grafana then you need to work through some tutorials. That can be a more difficult than it should be because the interface for using grafana keeps changing the the docs are normally way out of date. Unfotunately the grafana forum is often of little use as the developers do not seem to help there, so often questions go unanswered.
