how to add JPanel to auto generated netbeans JFrame?

I have a开发者_JAVA技巧uto generated netbeans GUI (JFrame) and I'm trying to add an external JPanel (different class) to the JFrame but it failed. What i'm supposed to do?

Note: JPanel is a web browser using DJ Native Swing.

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I would assume that you would add the JPanel to the JFrame's contentPane just as you would with a non-NetBeans GUI, but again we're sort of hamstrung until you can tell us what you've tried and how it failed.