How to register a new menu in dashboard and use it in the theme

Register Wordpress Menu

//in functions
function register_my_menus() {
  register_nav_menus(
    array(
      'new-menu' => __( 'New Menu' ),
      'another-menu' => __( 'Another Menu' ),
      'an-extra-menu' => __( 'An Extra Menu' )
    )
  );
}
add_action( 'init', 'register_my_menus' );

//in the theme
wp_nav_menu( array( 'theme_location' => 'new-menu', 'container_class' => 'new_menu_class' ) );