Prior to that, you need to create an ODBC using the "Connect" button in the script editor. If you already had done that, then use the button "Select" instead of the "Table file". There you will see a dialog with two main parts: the left one with the tables, views, etc, and the right one with the field names. Select and click on the "Add" button to generate the script.
You have got some free training and introduction to QlikView here.