showing external pages in content area

I found a script / program for setting up a classified section, and it’s contained within it’s own directory on my website. therefore I’m not sure how to incorporate it with my WP install. Is it possible to somehow call the index.php file into my WP content are? or someway make the classified index load there? just as if I were loading it into an iframe, except I don’t know enough about php to know if it can be loaded that way. any help would be fine 🙂 thanks! here is the url of the classified installation:

http://portfoliosfriend.com/jobs/