Hi there, the easiest option would be to use a plugin like – https://wordpress.org/plugins/duplicator/
However, if you’d rather do it manually you’ll need to download all the site content and pages/posts via tools>export from the WP admin area. Then import it into the new site you’ve setup which has WordPress and the theme already installed, via the tools>import option. Make sure you check the option when importing on the new site to include images.
Hope this helps.