Document how to access gerrit own metrics from Javamelody page

Change-Id: I79f4dc65daf62e75e69cc2978bb12198f1b8fcd3
diff --git a/src/main/resources/Documentation/about.md b/src/main/resources/Documentation/about.md
index f45afd3..725280d 100644
--- a/src/main/resources/Documentation/about.md
+++ b/src/main/resources/Documentation/about.md
@@ -8,3 +8,8 @@
 or the 'Administrate Server' capability.
 
 It adds top menu item "Monitoring" to access java melody page.
+
+Gerrit's own metrics can be accessed from within Javamelody monitoring page:
+`<gerrit_host_url>/monitoring?part=mbeans`. The pre-requisite for this is
+[JMX metrics plugin](https://gerrit.googlesource.com/plugins/metrics-reporter-jmx)
+that must be also installed.