WordPress Online

suppose i post a long article in wordpress that is on several pages, how can i convert it into several subpages so that the viewer can view the next part of the post by clicking on the page numbers below?
thanks

I want to keep my regular subpages on my site (example: mysite.php portfolio.php,) but I want to use wordpress as well for the theme and use my own subpages instead of the wordpress pages. How do I use my wordpress theme on my regular subpages?