Check out Customizing the Front Page of Your TRIBUS Ashland Theme Site for an introduction to Front Page widgets. Widgets are found in the Dashboard at Appearance->Widgets.
The TRIBUS Theme: Testimonials Widget lets you randomly showcase pre-selected client Testimonials on the front page of your site.
Testimonials are a special type of content, with their own section for adding, editing, and removing articles. Navigate to "Testimonials" in the Dashboard to view, edit, or add a new testimonial.
When creating or editing a Testimonial, check the box for "Feature This Review?" to include it in the lottery of Testimonials that will appear on the Front Page.