Widget / Index.php / Stylesheet / Front page

Hi. I am a newbie to WordPress but not to HTML.
Here is my site: http://www.beaconacademy.org/dev-wpbeacon/wordpress/

I want to put Our Mission and Alumni Stories to the right of the text and one on top of the other. So, basically another column or division. I am not sure if I need to change the Widget or Index.php or Stylesheet. Help appreciated!!!!

Thanks! Linda