When you need to capture user input that will be available to your installer then you need to use the UserInputPanel.
This panel allows you to prompt the user for data that you can use later in the installation process.
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There is a more complex example of a userInputSpec.xml from izPack v4 at at Sample userInputSpec.xml showing 3 panels. There are some advanced features in this example, but the general flow should be looked at first.
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