The creation of a window module requires two INT modules that are part of the INTViewer platform:
See the list of INTViewer modules to load the INTViewer platform and for a description of each module.
The window created will be a NetBeans "TopComponent" that is meant to be along the desktop area. For a window inside the desktop area, follow this other tutorial.
Click the green arrow in the Netbeans toolbar to run your customized INTViewer. Your component should be available from the Window menu of your customized INTViewer.