Make sure you have a sitemap.xml file in your project.
1. Locate your robots.txt file by typing http://www.yourdomain.com/robots.txt;
2. If you get a 404 error, you will have to create it the robots.txt file yourself in the top-level directory of your web server;
3. Enter the following into your robots.txt file: “Sitemap: http://www.yourdomain.com/sitemap.xml” and save it.