Important Note 28/05/14
The three columns of the 'homepage' template are coded with overflow: hidden; in the css. This might cause google to think there is some underhand 'cloaking' of content and to penalise your site. I don't know for sure and I don't know how you would find out, but if google position is important to you best correct it by using a plugin to insert extracts, or by just writing the extract in the template to make sure that text displayed on your page is the same as that displayed in the source.
This theme is taken from the html5 template Minimalism designed by Marija Zaric
The first, fixed width GetSimple Minimalism theme is still in extend here
The improved Responsive GetSimple Minimalism theme is now in Extend here.
The page template homepage.php includes the three columns. If you make three pages titled First, Second and Third with some paragraph text then an extract of the text will appear in the column on the homepage. The pages can be included in the menu or not as you like. Save the pages as First, Second and Third to establish the correct slugs, then changing the column titles with a simple edit to the template, and make the page titles what you like.
The default template is a plain page with sidebar.
I don't have it in use any more so there is no demo page.