add_action( 'admin_menu', 'admin_menu_olustur' );
function admin_menu_olustur() {
$baslik = 'R10 Uckan';
$menu = 'Uckan';
$menu_url = 'r10-uckan';
$menu_function = 'menu_icerik_function';
$favicon = ''.get_template_directory_uri().'/assets/img/favicon.png';
add_theme_page( $baslik, $menu, 'manage_options', $menu_url, $menu_function, $favicon, 60  );

}

function menu_icerik_function() {
echo '<h1>R10 Uckan</h1>';
}