Update the prometheus integration docs

This changes the prometheus integration documentation
to reflect the newest changes to the UI and funcionality
of all the features relevant to the monitor APM team

doc/user/project/integrations/prometheus.md

@@ -115,7 +115,7 @@ You can view the performance dashboard for an environment by [clicking on the mo
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/merge_requests/3799) in [GitLab Premium](https://about.gitlab.com/pricing/) 10.6.
 
-Custom metrics can be monitored by adding them on the Prometheus integration page. Once saved, they will be displayed on the environment performance dashboard provided that either:
+Custom metrics can be monitored by adding them on the monitoring dashboard page. Once saved, they will be displayed on the environment performance dashboard provided that either:
 
 - A [connected Kubernetes cluster](../clusters/index.md#adding-and-removing-clusters) with the environment scope of `*` is used and [Prometheus installed on the cluster](#enabling-prometheus-integration), or
 - Prometheus is [manually configured](#manual-configuration-of-prometheus).
@@ -300,8 +300,12 @@ Data from Prometheus charts on the metrics dashboard can be downloaded as CSV.
 
 For managed Prometheus instances using auto configuration, alerts for metrics [can be configured](#adding-additional-metrics-premium) directly in the performance dashboard.
 
-To set an alert, click on the alarm icon in the top right corner of the metric you want to create the alert for. A dropdown
-will appear, with options to set the threshold and operator. Click **Add** to save and activate the alert.
+To set an alert:
+
+1. Click on the ellipsis icon in the top right corner of the metric you want to create the alert for.
+1. Choose **Alerts**
+1. Set threshold and operator.
+1. Click **Add** to save and activate the alert.
 
 ![Adding an alert](img/prometheus_alert.png)