If you are making a one-page website, and you are going to use WordPress, create a WordPress “Page”, and put your content in it. Then in the Dashboard > Settings > Reading > Front Page Displays, select “A static page”, and choose the page you created.
To create a WordPress “Loop” within a page, you would normally use PHP to modify a page template [very different from a page], in a theme. Or use PHP to create a shortcode in a plugin that can be used in any theme. It is confusing though what you mean by: “a one-page website, and including a loop.” That doesn’t really make sense. A loop generally is used to sort through multiple pages and posts, via a query. I’ve never seen a one page WordPress site that uses a loop. What would you be looping through?
You can also set your front page to actually be a loop of posts in most themes. Just go to the Dashboard > Settings > Reading > Front Page Displays, select “Your latest posts”.