Before you start to develop a new action, please have a look at the available actions and screens. If it's just a few lines of code, you can use the "Run script" action to enter them directly into install4j. If you would like to collect user input, most use cases can be solved with a "Configurable form" screen.
An alternative way of adding your beans to the install4j is packaging them as an extension. In that case, you can select them directly from the standard registry dialogs instead of having to go through the "Search in custom code" menu entries when adding beans to the installer.
new File("user", "[file name]")For example, if you have added a native library jni.dll to your custom code, you can load it in a "Run script" action by calling
System.load(new File("user", "jni.dll").getPath());
After you have chosen your custom code locations, you will be able to select your own screens, actions and form components.