A first step in porting an application, especially one you don't really know, is to run the application in the NetBeans debugger and then take a GUI snapshot of it. That lets you relate the GUI elements in the application to their source code, very easily, as shown below for Wandora:
It's kind of similar to the Chrome integration for HTML5 applications! There, you can click in the browser and then see where items are defined in the IDE. In the above screenshot, you're actually doing something very similar, but then for Java desktop applications, whether in Swing or JavaFX.