Step 1: In your Website Builder, click Edit Site on the left.
Step 2: Scroll down to find the testimonials block. Should look like this.
Step 3: Select the content button on the top left.
Step 4: Click on the testimonial you want to change.
Note: You will see that there are two different places you can select. One section allows you to change the testimonial and the other allows you to edit the name the person who left it.
Step 5: Now you will want to write in the new content. Then select Update Content.
Step 6: Remember to Save and Publish your website!