wordpress add menu

menu-functions.php

function register_my_menus() {
  register_nav_menus(
    array(
      'footer-menu' => __( 'Footer Menu' ), //footer menu
      'extra-menu' => __( 'Extra Menu' ) //extra
    )
  );
}
add_action( 'init', 'register_my_menus' );

//on template
<?php wp_nav_menu( array( 'theme_location' => 'footer-menu' ) ); ?>
//wrapper class
<?php wp_nav_menu( array( 
    'theme_location' => 'extra-menu', 
    'container_class' => 'my_extra_menu_class', //wrapper calss
    'menu_class' => '',      //menu class
) ); ?>