How to implement WordPress into a design?

Heya all.

I’ve searched around here for a CMS. And I noticed there are alot of em, but alot of people recommended WordPress, so I thought I should try it out.

But, now that I’ve installed it (uploaded, database, etc) I wonder how do I use WP’s features, but using another design? At the moment the design is html and css, but it can easily, i hope, be converted to php.

So how do I actually get my own design, but with WP’s blogs, pages etc?
(And what part of WP is the templates? Is it the themes? My page is mainly graphics and tables/divs)

And, I used MM Contribute before, but it was extremly slow everytime, and it needed to be installed, so I’m in need of a web cms, so I and my friends can update anywhere.

Thanks for any tips or advices.