How to seperate my game screen from my login screen

Question

I want to call my login screen first so that the uer can have an account before playing the game. However i do not know where to call the login screen without having it interfere with the game:

So essentially every time the game wants to start it obviously opens the login screen first because they are all within the constructor. Anyone know how i can seperate the two different processes?

currently the set up looks like this:

private LoginScreen log;

    public FlappyBird() {
       
        
        //call login screen so that an account can be created
        log= new LoginScreen();
       
        log.setVisible(decision);
        
         
        Timer timer = new Timer(20, this);// used to ensure it repaints throught a schedule timer
        render = new FlappyBirdUI1();
        jframe = new JFrame();
        
        jframe.add(render);

        jframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        jframe.setResizable(false);
        
        jframe.setSize(new java.awt.Dimension(WIDTH, HEIGHT));
        jframe.setLocationRelativeTo(null);
        jframe.addMouseListener(this);
// set game screen to only be visible if the game button on home screen is clicked
        jframe.setVisible(true);

        //using a rectangle as the "bird"
        
        bird = new Rectangle(WIDTH / 2 - 10, HEIGHT / 2 - 10, 20, 20);

        pipes = new ArrayList<Rectangle>();
        addpipe(true);
        addpipe(true);
        addpipe(true);
        addpipe(true);

        // gsettings.setBounds(0, HEIGHT, 30, 25);
        timer.start();
         
    }