you'll see it in the theme you use....check out a file like index.php... (also, one thing I forgot, if the page you made is a .html page, you'd need to rename it to .php for the include code above to work)
<?php get_header(); ?>
gets the header
<?php get_sidebar(); ?>
gets the sidebar....you get the idea.
Also if you want your page's styling to match the rest of your site well, you may have to use the same classes/divs in places on your stand alone page.... (this is what would call in your actual css styles)
---does your page need to be a standalone page? Like because of URL or something? Another option you have is to just make a page within WP, and make a custom page template in your theme by copying one of your templates (like page.php), deleting the loop, inserting your custom code, and assigning the template to the page you made