Modification nav menu

Hi,

I want to modificate my my default nav menu with one that I’ve created in WordPress Menu Manager (nav-menu.php).

My template is Traction. How can I remplace the default with the new ?

I’ve add this code in funcion.php :

<?php wp_nav_menu( array( 'sort_column' => 'menu_order', 'container_class' => 'menu-header' ) ); ?>

And how to activate it now im my template ?

My website : http://www.webkef.com/en