How to Hide the "OO Cleaner for CFDB7" Admin Menu

function plt_hide_oo_cleaner_for_cfdb7_menus() {
	//Hide the "Settings → OO Cleaner for CFDB7" menu.
	remove_submenu_page('options-general.php', 'oo-cleaner-for-cfdb7');
}

add_action('admin_menu', 'plt_hide_oo_cleaner_for_cfdb7_menus', 11);

Where do I put this code?