1. Navigate to the ch11-hello-world folder of the WordPress plugin directory of your development installation.
2. Open the ch11-hello-world.php file in a text editor.
3. Add the following line of code at the end of the file to register a function to be called when WordPress is building the administration page's menu:

add_action( 'admin_menu', 'ch11hw_settings_menu' ); 

4. Add the following code section to provide an implementation for the ch11hw_settings_menu function:

function ch11hw_settings_menu() { 
    add_options_page( 
        __( 'Hello World Configuration', 'ch11hw_hello_world' ), 
        __( 'Hello World', 'ch11hw_hello_world' ), 
       'manage_options', 
       'ch11hw-hello-world', 'ch11hw_config_page' ); 
} 

5. Insert the following block of code to create the ch11hw_config_page function declared in the call to add_options_page:

function ch11hw_config_page() { 
    $options = get_option( 'ch11hw_options' ); 
    ?> 
 
    <div id="ch11hw-general" class="wrap"> 
    <!-- Echo translation for "Hello World" to the browser --> 
    <h2><?php _e( 'Hello World', 'ch11hw_hello_world' ); ?></h2> 
  
    <form method="post" action="admin-post.php"> 
    <input type="hidden" name="action" 
           value="save_ch11hw_options" /> 
    <?php wp_nonce_field( 'ch11hw' ); ?> 
 
    <!-- Echo translation for "Hello World" to the browser --> 
    <?php _e( 'Default Text', 'ch11hw_hello_world' ); ?>: 
    <input type="text" name="default_text" 
           value="<?php echo 
                   esc_html( $options['default_text'] ); ?>"/> 
    <br /> 
    <input type="submit" value="<?php _e( 'Submit', 
        'ch11hw_hello_world' ); ?>" class="button-primary"/> 
    </form> 
    </div> 
<?php } 

6. Add the following line of code to register a function to be executed when the administration panel is being prepared to be displayed:

add_action( 'admin_init', 'ch11hw_admin_init' ); 

7. Append the following code segment to provide an implementation for the ch11hw_admin_init function:

function ch11hw_admin_init() { 
     add_action( 'admin_post_save_ch11hw_options',
                 'process_ch11hw_options' ); 
} 

8. Provide code for the process_ch11hw_options function, declared in the previous step, by inserting the following code:

function process_ch11hw_options() { 
    if ( !current_user_can( 'manage_options' ) ) {
          wp_die( 'Not allowed' );
    }

    check_admin_referer( 'ch11hw' );
 
    $options = get_option( 'ch11hw_options' );     
    $options['default_text'] = $_POST['default_text']; 
 
    update_option( 'ch11hw_options', $options ); 
    wp_redirect( add_query_arg( 'page', 'ch11hw-hello-world', 
                     admin_url( 'options-general.php' ) ) );
    exit; 
} 

9. Save and close the plugin file.
10. Navigate to the administration page of your development WordPress installation.

11. Click on the Reglages (Settings in French) section on the left-hand navigation menu to expand it. You will see a new menu item called Hello World in the tree. Selecting the new entry displays the plugin's simple configuration form, as shown in the following screenshot: