Note: You must have an account with a Google in order to connect your site to Google Webmaster Tools.
1. Go to Google Webmaster Tools and sign into your Google account, click the red button to add your website.
2. Once you've clicked the button to add your site, just type your website's URL in the box. Click the blue button to continue.
3. Get the code. You will want to use the HTML tag under the Alternative Method. Only copy the code that is in the parenthesis after content, as per the image below.
4. Log in to your prestashop site and open the Website Verification Module, paste the copied code into the Google ID field and click save.
5. Switch back to Google Webmaster Tools and click 'Verify'.
Congratulations! You've connected your website to Google Webmaster Tools! Now that you've verified and connected your website, you can submit your sitemap!