Rendering a 2d image in java

I am fairly new to java programming and I am trying to make a simple game however, I need to render my image I have made here is the code I put in eclipse:

public class MainMenu extends JFrame{
 public static void main(String[] args){
        new MainMenu(); 

 }
 public MainMenu(){
     this.setSize(300, 450); 
        this.setLocationRelativeTo(null);     
        this.setResizable(true); 

        Toolkit tk = Toolkit.getDefaultToolkit(); 

        Dimension dim = tk.getScreenSize(); 

        int xPos = (dim.width / 2) - (this.getWidth() / 2);
        int yPos = (dim.height / 2) - (this.getHeight() / 2);

        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        this.setLocation(xPos, yPos); 

        this.setTitle("Frame For Flamedash Testing");

        this.setVisible(true); 
 }
 public void paint(Graphics g){   
        Image img1 = Toolkit.getDefaultToolkit().getImage("mainmenuscreen.png");
        g.drawImage(img1, 20, 20, null);
 } // public void paint(Graphics g)

 public void putit() {
     boolean MainMenu = true; 

     while (MainMenu == true){
         repaint(); 
     }

}
}

When I put that it is all fine and it does not give me any errors what so ever then I run it and it shows the frame but shows no picture than I full screen it because I set re-sizable true and it shows the default color in one spot with the size I set the frame too and another one identical but on the corner and black everywhere else. Any help to rendering this .png image will help, thank you in advance.