Looking at this guide, it seems that you just need to add some meta tags to your header (or footer, maybe).

Typically, these files are located at /includes/templates/<your_template>/common/html_header.php

If you open that, you should see something similar to this:

Code:
. . .
 * @license http://www.zen-cart.com/license/2_0.txt GNU Public License V2.0
 * @version $Id: html_header.php 19537 2011-09-20 17:14:44Z drbyte $
 */
/**
 * load the module for generating page meta-tags
 */
require(DIR_WS_MODULES . zen_get_module_directory('meta_tags.php'));
/**
 * output main page HEAD tag and related headers/meta-tags, etc
 */
. . .
Put your meta tag where all the other meta tags are.