How to Hide the "Image Optimizer" Admin Menu

function plt_hide_image_optimizer_wpssk_menus() {
	//Hide the "Settings → Image Optimizer" menu.
	remove_submenu_page('options-general.php', 'imagopby');
}

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

Where do I put this code?