Problems moving a blog to root folder

I’m trying to follow the instructions given here to give wordpress its own directory but have it live in the root of my site: http://codex.wordpress.org/Giving_WordPress_Its_Own_Directory

However, in General Settings when I try and edit WordPress Address (URL) or Site Address (URL) boxes, they are not clickable, they’re greyed out. Here’s a screenshot.

Why is this happening? What can I do?

Thanks-