Mailpress: styling with Atahualpa

I've reinstalled my mailpress after moving to ATA theme and I wonder how I can set my mailpress to look like the page/post style.
Mailpress provides two solutions for this:
use the category.php of the file or a template they have to make it look like a page (basically page.php)
Since both files arent in the atahualpa theme, how should I proceed?

Is there a better solution than going into the css.php file and change the hardcoded strings and tags??