added verification step for enabling N+ API using CSG

Author: travisamartin

content/includes/use-cases/monitoring/enable-nginx-plus-api-with-config-sync-group.md

@@ -14,4 +14,5 @@ files:
 
 {{< include "config-snippets/enable-nplus-api-dashboard.md" >}}
 
-7. Select **Next**, review the diff, then select **Save and Publish**.
+7. Select **Next**, review the diff, then select **Save and Publish**.
+8. Open your browser to `http://<instance-ip>:9000/dashboard.html` (replace `<instance-ip>` with the IP or hostname of one of your group members). You should see the NGINX Plus dashboard.