Changing Theme for wordpress.

[Casteloes]

Does anyone knows how to change the ilacrimo theme for wordpress. I have a problem because i want to add 468*60 banners in middle of the post but this size is too big to theme. The zone for posts are little than that size banners as you can see in this post.
http://www.webvicio.com/2007/wordpress-23/


Here is download link for css style file for this theme.
http://rapidshare.com/files/59718412/style.css.html