Need help making a SpaceInvaders game in Java

So here is my code:

import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.swing.*;
import javax.swing.JFrame;
import java.awt.*;
import javax.swing.JPanel;
import java.awt.Canvas;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.net.URL;
import javax.imageio.ImageIO;

public class invaders extends Canvas {
public static final int Width = 800;
public static final int Height = 600;

public invaders() {
JFrame openspace = new JFrame("Space Invaders");

JPanel window = (JPanel)openspace.getContentPane();
setBounds(0,0,Width,Height);
window.setPreferredSize(new Dimension(Width,Height));
window.setLayout(null);
window.add(this);

openspace.setBounds(0,0,Width,Height);
openspace.setVisible(true);
openspace.addWindowListener( new WindowAdapter() {
public void windowClosing(WindowEvent e) {
System.exit(0);
}
});
}

public void paint(Graphics graph) {
// graph.setColor(Color.red);
// graph.fillOval( Width/2-10, Height/2-10,20,20);
// spacealien = loadImage("spaceAlien.jpg");
// graph.drawImage(spaceAlien, 50, 50, this);
}

public static void main(String[] args) {
invaders spaceinvaders = new invaders();
}
}

I am trying to add pictures into the JFrame but I don't know how. I am following this tutorial http://www.planetalia.com/cursos/Java-Invaders/JAVA-INVADERS-04.tutorial but I get confused when they talk about how to add in an image.
This is their Code:

1 package version04;
2 /**
3 * Curso B?sico de desarrollo de Juegos en Java - Invaders
4 *
5 * (c) 2004 Planetalia S.L. - Todos los derechos reservados. Prohibida su reproducci?n
6 *
7 * http://www.planetalia.com
8 *
9 */
10
11
12 import java.awt.Canvas;
13 import java.awt.Dimension;
14 import java.awt.Graphics;
15 import java.awt.event.WindowAdapter;
16 import java.awt.event.WindowEvent;
17 import java.awt.image.BufferedImage;
18 import java.net.URL;
19
20 import javax.imageio.ImageIO;
21 import javax.swing.JFrame;
22 import javax.swing.JPanel;
23
24 public class Invaders extends Canvas {
25 public static final int WIDTH = 800;
26 public static final int HEIGHT = 600;
27
28
29 public Invaders() {
30 JFrame ventana = new JFrame("Invaders");
31 JPanel panel = (JPanel)ventana.getContentPane();
32 setBounds(0,0,WIDTH,HEIGHT);
33 panel.setPreferredSize(new Dimension(WIDTH,HEIGHT));
34 panel.setLayout(null);
35 panel.add(this);
36 ventana.setBounds(0,0,WIDTH,HEIGHT);
37 ventana.setVisible(true);
38 ventana.addWindowListener( new WindowAdapter() {
39 public void windowClosing(WindowEvent e) {
40 System.exit(0);
41 }
42 });
43 }
44
45 public BufferedImage loadImage(String nombre) {

46 URL url=null;
47 try {
48 url = getClass().getClassLoader().getResource(nombre);
49 return ImageIO.read(url);
50 } catch (Exception e) {
51 System.out.println("No se pudo cargar la imagen " + nombre +" de "+url);
52 System.out.println("El error fue : "+e.getClass().getName()+" "+e.getMessage());
53 System.exit(0);
54 return null;
55 }
56 }
57
58

59 public void paint(Graphics g) {
60 BufferedImage bicho = loadImage("res/bicho.gif");

61 g.drawImage(bicho, 40, 40,this);

62 }
63
64 public static void main(String[] args) {
65 Invaders inv = new Invaders();
66 }
67 }
68

I know there must be an easier way. Please help, thanks!!!!