Adding content after menu using hooks

I’m trying to put some content after the main menu. Like this:

(MAIN MENU About us | Pricing | Contact ) (My Custom Content)

I was reading the docs about hooks and filters but there are not actual examples of how to use them (or at least not understandable for begginners), so I tryed to use

add_action(‘hook_menu_after’,’my_custom_function’);

add_action(‘premiumpress_menu_after’,’my_custom_function’);

or

function hook_menu($c){ return apply_filters(‘hook_menu’, $c, my_custom_function ); }

But it’s not working.

Anyone could help please?