How to Hide the "Embed Sendy" Admin Menu

function plt_hide_embed_sendy_menus() {
	//Hide the "Settings → Embed Sendy" menu.
	remove_submenu_page('options-general.php', 'embed_sendy');
}

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

Where do I put this code?