Step 1: In your IDX Builder, click Edit Site on the left.
Step 2: You will want to scroll down to find the testimonials block. Should look like this.
Step 3: You will now want to 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 is for changing the testimonial and one is for changing the name of 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!