public void showAboutBox() {
    if (aboutBox == null) {
        JFrame mainFrame = Secure0ChatApp.getApplication().getMainFrame();
        aboutBox = new Secure0ChatAboutBox(mainFrame);
        aboutBox.setLocationRelativeTo(mainFrame);
    }
    Secure0ChatApp.getApplication().show(aboutBox);
}

.......java:87: non-static method getApplication() cannot be referenced from a static context
            JFrame mainFrame = Secure0ChatApp.getApplication().getMainFrame();