A Joomla template is not a website and can not be considered a completed website design. The template is the basic foundation for the design of your Joomla website.
A Joomla template doesn't contain sample data which is used on the template demo page. The sample data should be installed in your website, and this will make your joomla website look like the template demo.
Out latest templates have quickstart packages, created with Akeeba Kickstart. The instillation of quickstarts is done in less than three minutes. First unzip the quickstart which is inside the template package and use FTP to add it in your website. If you have not done yet your website and already have joomla installed, replace all joomla files with the ones which are in quickstart. After go in your website and make the installation by following all the steps.
Important: If you have live website already running, should install only the template. However you will get the other site layout with new template so all modules have to be assigned to new template layout.