The Mezmo Prometheus Remote Write source provides a unique endpoint URL that uses Bearer Token authentication. You can obtain the unique endpoint and Bearer Token from the Mezmo pipeline app when you create a new Prometheus Remote Write source.
If you are running Prometheus within Kubernetes using the Kubernetes operator you can configure the instance with these commands, templating in the Bearer Token, the endpoint provided by the Mezmo Web App, and the Prometheus crd name:
kubectl -n monitoring create secret generic mz-prom-rw-token --from-literal=value=<TOKEN FROM APP>