How to Hide the "reSmush.it" Admin Menu

function plt_hide_resmushit_image_optimizer_menus() {
	//Hide the "Media → reSmush.it" menu.
	remove_submenu_page('upload.php', 'resmushit_options');
}

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

Where do I put this code?