Header to go across the page

Hello! I am just finishing up a class on wp.org and wanted to use the Catch Everest theme to create a children's author's website similar to the site www.marylosure.com which also uses the Catch Everest theme, but when I try to upload a header it comes out like this: www.blog.carolyncarmody.com. I also wanted to get the three columns off the front page but do not see an option to do that. Thanks