Register menu in wordpress

functions.php

<?php

function register_menu() {
register_nav_menu('primary-menu', __('Primary Menu'));
}
add_action('init', 'register_menu');
?>


header.php:

<?php if ( has_nav_menu( 'primary-menu' ) ) { /* if menu location 'primary-menu' exists then use custom menu */
      wp_nav_menu( array( 'theme_location' => 'primary-menu') );
} ?>