Two row notification is only supported in Jelly Beans (Android 4.1) and above in the form of expandable / collapsible widget.
In the main app, click the Notification Widget icon and you can enable/disable 2nd if your device supports this feature.
Also note that the android OS may choose to collapse the notification to a single row based on the availability of space. Try pinch-zooming (using two fingers) on the notification widget to expand.
This feature is not available in older android versions (android 4.0 and before).