import java.awt.Color;
import java.awt.Component;
import java.awt.Container;
import java.awt.Frame;
import java.awt.event.*;

import javax.swing.*;
import javax.swing.text.AbstractDocument.Content;

public class Window extends JFrame implements KeyListener{

public static void createAndShowGUI() {
	
	JFrame frame = new JFrame("Tetris");
    frame.getContentPane().add(new Rules());
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    frame.setSize(600, 800);
    frame.setFocusable(true);
    frame.setVisible(true);
    frame.setResizable(false);
  
    Container content = frame.getContentPane();
    content.setFocusable(true);
    content.setBackground(Color.black);
    
    }

public void keyListener(){
	
	}

public static void main(String[] args){
	
	 javax.swing.SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            createAndShowGUI();
        }
    }
        );
}
	

public void keyPressed(KeyEvent e) {
	
	int keyCode = e.getKeyCode();
	System.out.println(keyCode);
	
	if (e.getKeyCode() == 37){
		Rules.moveLeft();
	}
	

}

public void keyReleased(KeyEvent e) {

}

public void keyTyped(KeyEvent e) {
	
}

 

}

So how am I supposed to add KeyListener to this code? I've tried to add it about everything, but I always an error such as "can't use this in a static content". I'm trying to get the console to print out the keycode when I type in a key.

halp?

Ideally you should put the GUI in a separate class from the driver with the main method. In this simple example you can easily fix your problem by putting everything you have in createAndShowGUI to be a constructor for the GUI, like this:
http://pastebin.com/5iDatWaJ