Modifying page content and layout

I am interested in making the alternative pages three columns instead of 2 like the template has been designed. The homepage is ok with 2 columns, you can see it here http://www.bicyclenerd.com/wordpress

But on the alternate pages I want to creat 3 columns :: http://bicyclenerd.com/wordpress/?page_id=6

I cannot figure out what files to add or change the css. I can modify the index page ok… but that is all.

here is an example of a layout i am trying to replicate.

http://www.floydlandis.com

Thanks,

CT