If you already have a html file from your design, and are using stock drupal, then the info on these pages (Convert any website layout or template into a Drupal theme - easily! and Assigning content to regions) of the theming guide will get you along.
In short, there are the following regions;
Drupal outputs this content in
So if you place a
<?php print $left ?> (or any other one) in you html layout will output 'left' content to your design.
There are other additional strings that are output so just make sure you put those in your html (Check out a
page.tpl.php, to get an idea).
How to get your html to initially display without making a whole theme? Just copy the relevant pieces of your html design to a (copy) of
...and read the Theme Guide.