There are two ways to do it.
One is that you develop (or hire someone to develop) a WordPress theme that matches your Web site. Depending on how elaborate your design is, it may take an experienced developer between one day and two weeks.
The other way is for you to fold your existing site into WordPress. As you may know, WordPress allows you to create Pages, which exist outside the flow of the blog and form a hierarchy of their own, in addition to blog posts. So what you can do is to take your existing pages and copy their content into WordPress pages. That way, your entire site, not just the blog, will be managed through WordPress.
check out this tutorial I wrote a while back… Dreamweaver Templates into WordPress Themes… it’s based around Dreamweaver but if you read between the lines and think outside the box a little.. you should be able to patch it together.
Good luck..
PS. Post comments on Search Friendly Web Design if you need help with the tutorial… I usually respond within 24 hrs.
