Login to Bongo4U Admin Mode.

Hover over the "Testimonials..." option on the Page menu, then hover over the testimonial to be edited, and click on its name.

You will see the Edit Testimonials form.

Change any of the fields as desired.

Click any of the "?" help links beside each field for details or suggestions.

Click the [Save Changes] button to store your revisions.

Additional Info: Read the "How do I display Testimonials on my site" entry.