Moving 'Leave A Reply' to bottom of post in Twenty Twelve

Do not edit the Twenty Twelve theme. It is the default WordPress theme and having access to an unedited version of the theme is vital when dealing with a range of site issues. First create a child theme for your changes.

Thanks, I understand the importance of leaving the theme intact and already have a style.css file set up for a couple of other things but not sure the code to move the ‘Leave a Reply’ link.

or is moving this more than just having extra css code?

Yes – this would involve creating customised versions of the parent theme’s template files.