Problem with admin panel menus

Hello, the option “menus” to set dinamic menus on my theme are not in my admin panel.
I have already add the code in function.php, the code who wordpress developer page are informing, this one:

function register_my_menu() {
    register_nav_menu('header-menu',__( 'Header Menu' ));
  }
  add_action( 'init', 'register_my_menu' );

its the same code, but the option “menus” stills hide, how can i fix it ?

I’m brazilian, and dont speak english very well, so ignore the gramatical erros please..

• This topic was modified 3 years, 4 months ago by bcworkz. Reason: resolved