Within the Visibility settings of your Review Stage, you can modify the Application information that you wish to be visible within the reviewer portal. You can modify the information that appears on the reviewer's list of assigned applications, as well as additional information to appear within the Summary of the application.
Adding additional details to the reviewers portal will provide your reviewers with more information on the applications up front.
Any information that is added to the Application Summary is accessible when the reviewer clicks to access the split screen of the application.