I would recommend looking at the Viz Guide Example Workbook. There is a nice example on the Map tab. If you select that map, then go to the menu and select Data Table > Edit, you will see the data source connection including, in this case, the Excel file that is used to drive that Map. It is normally installed in the My Documents > Datawatch Desktop > Data folder. This will provide an example of how the data file that is driving the map is structured.