Testimonials are similar to product reviews, except they are about your whole store and not specific to a single product.
Testimonials are essentially store reviews.
In order to show your testimonials, you need to add a testimonial widget to your site.
How to add a testimonial widget
Find the Widget section on the left-hand side of your dashboard
Click the + Add Widget button
Select Show Something Else
Type in 'Testimonials' in the search bar
Click the Increase Trust drop-down menu
Select Testimonial Carousel
Now, you need to decide where you want to show your testimonials. You can show them on your:
Once you decide where you want to show your testimonial
When you are ready to show your testimonial, click the green Launch button