The premium version of the plugin comes with a feature that lets you require admin approval before a submitted review is displayed on your site.
To enable this feature, go to Settings > Premium, scroll down to the RESTRICTIONS section and toggle on the Require Admin Approval option.
With that option enabled, the reviews area in the admin will now be divided into two pages.
The Approved Reviews page shows all reviews that are currently published on your site.
The Awaiting Approval page shows all reviews that have been submitted, but not yet approved. With the Require Admin Approval option enabled, when a new review is submitted, the post is set to draft status. To approve a new review, go to the Awaiting Approval page, click on a review and then click the Publish button. The review will now be published and visible on your site, and will now show on the Approved Reviews page in the plugin admin.