The Reviewers/Referees tab is where you can add key quotations from reviewers and referees:
Fill in the fields as displayed above; there is space for 6 reviews. None of this information is compulsory, but it will certainly benefit you to increase the content aligned with your books. It is valuable marketing.
It can also help your editorial department support its pitch to the sales department when trying to add further projects into the printing and production schedule.
When finished, click on the Update tab. You are ready to move onto the next tab: manipulating the editorial schedule.