Change design for frontend page

I have trying for hours to change layout for the frontend registration page, but can not find which php and/or xml files set the layout.
Here is the page i want to change: http://brfrabatten.se/index.php/news-events/prenumerera

I want to get rid of the sign up box and just use guest subscription. I also want to translate the language.
Can you guide me?
Thanks in advance