The documentation tells you:
https://docs.zammad.org/en/latest/appendix/reporting-tools-thirdparty/grafana.html#setting-up-required-data-sources
If that’s not good enough because you e.g. have Grafana on a different machine than Zammad, then I’m afraid I won’t help you. The data within Elasticsearch are very sensitive and incorrect protection of these will lead to disasters. Please consult the elastic documentation in such a case. They have you covered.