craig.johnson.1991 on "Contact page CSS location"

Hi I am recently new to WordPress and have used the default contact page template at http://amy-and-duncan-are-getting-married.co.uk/contact/

I want to be able to tweak the CSS of the captcha that I have moved underneath the message box but when in Chrome and right click "Inspect Element" it says the CSS that this code is stored in is called page_template.css.

I apologise if this is a stupid question but where can I locate this file?

Thanks
Craig