how to achieve two columns layout? (child theme)

i’m designing a site with the twenty eleven child theme but now my client wants columns under the video, not beside it. i’m not sure how to accomplish what he wants.

here is the site i’m working on: http://www.lizartlizard.com/lltest
password is: demo
(this is my demo site)

here is a sample of how he wants it to look: http://www.kunstgras.mobi/

if this can’t be done with the twenty eleven theme, perhaps you could suggest a better framework that looks more like this one?