Sitemap.xml consists of the internal architecture of your website. It becomes easier for search engine bots to add your website as they will get the right information in very specified manner. Check if your site already has sitemap if it does not then create sitemap.xml for your site.
Go to XML Sitemap Generator and enter your website details (URL) and choose frequency “Monthly” then click on Start. After few moments, the sitemap will be generated. It actually depends on upon how many links are there for your website. Then Download sitemap.xml and then upload it to your root directory.