Suppose we register a menu using  register_nav_menus function in php with a id ‘header_Menu’,  , then we can call the menu as below

<div id=”menu”>
<ul id=”dropmenu”>
<?php wp_nav_menu( array( ‘container’ => false, ‘theme_location’ => ‘header_Menu’, ‘items_wrap’ => ‘%3$s’ ) ); ?>
</ul>
</div>