In your theme functions.php
you should register the menu location by adding the following code:
register_nav_menus(
array(
'menu_1' => 'Menu name #1',
'menu_2' => 'Menu name #2'
)
);
For more instruction about the register_nav_menus()
function you can visit the related codex.
Then in your theme files, you should use the following code:
wp_nav_menu(
array(
'menu' => 'menu_1'
)
);
For more instructions about the wp_nav_menu()
function you can visit the related codex.
Finally, the sub menu items can be manipulated from within the WordPress dashboard. You can see this video for more information.