All the page are provided in this template, without those list page who has single page like blog page, all the content comes from data folder. After open the data folder you will see all page contents file, like homepage.yml for homepage, about.yml for about page.
You can easily change the demo content with your won content, just remember that you have to follow the indent that are provided in demo content. If you miss the indentation will get an error. So carefully copy the loop, and change your content. Every loop starts with - this symbol.
Contact page email address provide in themes>static>mail.php file.