wow..i tought you were a L33T HaXOR trying to hack in a site
well what you need is what we call an ADMINISTRATION PANEL or CONTROL PANEL.
And you can't just do one. First of all your site needs to be dynamic not static html. Secondly if it's dynamic and it fetched data from a database, you need to create the admin panel to use the same database, fetch data from it and allowing you to edit the db. Not an easy job but it can be done. All you need is some determination, read a couple of tutorials/books on php/mysql and you'll be set. Then come here with your problems and we'll help you.
Damian