In Wordpress there's a menu option called 'Appeareances'. I want to add (e.g.) a submenu 'header' there and then be able to customize the header from within wordpress (administration page).
From what I understood I have to have a 'functions.php' file in my theme folder. In the 'functions.php' file I write something like this:
<?php add_submenu_page( $parent_slug, $page_title, $menu_title, $capability, $menu_slug, $function); ?>
Of course with adapted arguments (which I'm not entirely sure what those should be since I feel quite lost in all this).