add_action( 'admin_menu', 'register_my_custom_menu_page' );
function register_my_custom_menu_page() {
// add_menu_page( $page_title, $menu_title, $capability, $menu_slug, $function, $icon_url, $position );
add_menu_page( 'Custom Menu Page Title', 'Custom Menu Page', 'manage_options', 'custom.php', '', 'dashicons-welcome-widgets-menus', 90 );
}