I want to add some home-made features to WP Admin. For example, I'll be coding in a couple fields that are mandatory. They're treated just like custom field keys and values, but they're preset and required.
What I want to know is what file I need to work with to edit the different admin section pages. post.php seems to be the one I browse to in my browser, but I didn't find anything there to edit.
Help would be greatly appreciated.