Step 1. Log into your admin and go to Modules » Google Add-Ons » Generate Google Site Map
Step 2.
Right click on the xml file link and select Save Target As... to save the file to your local machine.
Step 3 : Upload the file sitemap.xml to your site via FTP at the root level.
Step 4. Go to Google Webmaster Tools at https://www.google.com/webmasters/ and sign in to your Google account.
Step 5. Click your domain or click ADD A SITE if you haven't registered your site yet.
Step 6. Click Sitemaps.
Step 7. Click Add/Test Sitemap.
Step 8. Enter your sitemap file name : sitemap.xml and click Submit Sitemap button.
You are done!
Google may take some time to detect and process your sitemap.