Added missing part about telling the dashboard plugin to use the custom aggregator

git-svn-id: https://svn.apache.org/repos/asf/maven/maven-1/plugins/trunk@114408 13f79535-47bb-0310-9956-ffa450edef68

dashboard/xdocs/authoring.xml

@@ -55,6 +55,14 @@ maven.dashboard.aggregator.[aggregator name].artifact = [Location of artifacts f
 maven.dashboard.aggregator.[aggregator name].label = [Label to display in report]
 maven.dashboard.aggregator.[aggregator name].goal = [Goal to call that generates the artifact above]
 ]]></source>
+        <p>
+          In order to use your aggregator in the dashboard report, you need to 
+          add it to the list of aggregators by adding the following property in
+          your <code>project.properties</code>:
+        </p>
+<source><![CDATA[
+maven.dashboard.aggregators = [aggregator name],[other aggregators to use]
+]]></source>        
       </subsection>
       <subsection name="Step 3: Tips">
         <p>