Sub menus are not displayed under menu

See more:

CSS

HTML

PHP

WordPress

I have created my own theme in wordpress and i have added below mentioned pages in that theme

header.php
footer.php
index.php
sidebar.php
functions.php
page.php
style.css

In functions.php i have written this code

<?php
function register_my_menu()
{
register_nav_menu('Primary-Menu',__( 'Primary Menu' ));
}

add_action( 'init', 'register_my_menu' );
/* end of code */
 /*by writing this line menu displayed on theme  menu code finished */
?>

<?php
  register_sidebar(array (
'name' => __( 'Primary Widget Area'),//__ returns the translated text
'id' => 'widget-name',
'description' => __( 'The primary widget area'),
'before_widget' => '<li id="%1$s" class="widget-container %2$s">',
'after_widget' => "</li>",
'before_title' => '<h3 class="widget-title">',
'after_title' => '</h3>',
) );
add_action( 'widgets_init', 'register_sidebar' );//function to load my widget


    if ( function_exists('register_sidebar') )
    register_sidebar(array('name'=>'Welcome Message','before_widget' => '','after_widget' => '',
                    'before_title' => '<h1>','after_title' => '</h1>',));
    register_sidebar(array('name'=>'Top Ten Articles','before_widget' => '','after_widget' => '',
                    'before_title' => '<h4 class="top-ten">','after_title' => '</h4>',));
    register_sidebar(array('name'=>'Reviews','before_widget' => '<div id="reviews">','after_widget' => '</div>',
                    'before_title' => '','after_title' => '',));
?>

My menu and sub menus are visible on theme but sub menus are not coming under the mentioned menu.
What to do??
Thanx in advance