How to configure Prometheus on Gitlab Ruuner?


I have Gitlab Omnibus 9.4 CE running on a Ubuntu Linux machine.
I have Gitlab Multiple Runner 9.2 running on some Linux machines and Windows machines as well.
I’ve already configured Gitlab to use Prometheus monitoring and it’s working fine.
Now, I want to monitor my runners, but I can’t get it to work.
I don’t know what to add in the metrics_server line. I don’t know how to scrape this data. This is a bit different from what I’ve already done with Prometheus, installing exporters as services and adding the configuration to the prometheus.yml file. I don’t see the metrics page.
Is there any way that I show these data on Grafana?
I’m stuck here. Would you please help me?
Thanks in advance.