Hi Krunal,
the data sources need to be populated by the website. In the most common scenario, your website is published via a CMS (content management system) so you would code your CMS templates to build and populate the data object and the utag.js include. We also have several plugins that can be added from the CMS side (such as the Wordpress Tealium iQ plugin) that handle most of the template coding for you (I say most because you may have edge cases that need to be manually developed for outside of the plugin).