Pro Sites

How can I customize the wording, formatting, look and feel, etc., that are displayed (for example) when a user goes to http://webuildfreewebsites.com/wp-signup.php and as they continue forward on each of the pages.

I guess it would have been nice if each page was automatically created in the Wordpress installation so I could just go to the pages and make the changes I wanted. But I don't see this.

So, how can I modify any and all of the pages that come up during the process as a user signs up, and/or as they go through the process of selecting add-ons, etc.?

Help?

Gary