My theme seems to be using a script that I can’t find?

I am using the Carrington theme as my base for my site. I want to change the header to be a clickable header and I found how in the codex.

However when I dove in to look for the code, the Carrington theme info seems to just have a line containing:

<?php

if (__FILE__ == $_SERVER['SCRIPT_FILENAME']) { die(); }

cfct_error('404');

?>

First off, is it kosher for me to change carrington code for my site, and secondly, how do I find the code I need to change the site? Lastly, do you edit your code in your blog or off line in a separate program?

Thank you, from an XHTML noob – Vanessa

EDIT:

I think I found it in the CSS folder. However, I am still wondering where people edit this info, and if it’s ok to edit it at all. What program do you use for editing? I am embarrassed to say I have Adobe golive, would that be where I would want to edit?