I managed to add xy coordinate in GeoExplorer, I use OpenGeo suite to use GeoExplorer. I added the OpenLayers mouse position code to the composer in order to show the coordinates. Please consider my previous question and answer:
how to show coordinate on a geoexplorer map by moving the mouse?
The problem is, when I publish my map and use iframe tag the coordinate system will disappear. I even changed the "viewer" to "composer" in iframe tag, but still no result.