The Testimonial is part of the avvin theme. You can setup it very easily. Here are steps.

• To setup Testimonials, first you need to add some entries with photos and texts. Go to "Testimonials" section and click "Add New". Fill details as described in below screenshot:
  
• Create some more entries as described above.
• Now we need to create a new page to show our Testimonials. The option is included in "Visual Composer" plugin (Make sure you installed Visual Composer plugin). Go to Pages >> Add New and click on "Add element" button:
  
• You will see all Visual Composer elements. Click on ThemetechMount Testimonial Box option:
  
• Now you will see options for the Testimonial area. Just modify the option are your requirements and click on "Save" button to apply the changes:
  
• The Testimonials box is inserted. The box will look like this:
  
• That's it.