Simply nest your JPanels. Create a new JPanel, say called northPanel, that uses a BorderLayout, and add it to the main window in the BorderLayout.NORTH position, and then add your JFIleChooser to this northPanel JPanel in its BorderLayout.WEST position.
Option 2: give the northPanel a BoxLayout that is oriented along the line axis, add the JFileChooser, and add glue.