Step by Step : 

Step 1— Go to Branding

• From the left menu, click on Branding under Settings & Customization.

• Select Review widgets, and click on the setup widget.

Step 2 — Navigate the review widget

• From the Review widgets page, 

• Find the Review widget and click on customize.

Step 3  — Choose Layout

• Select the layout style for your review widget. (Grid or list)

Step 4  — Save Changes

Once customizations are done, click Save Changes at the bottom.