First, to access the reviewer's email address your company will need to have a company user account which will allow you to log into your company tools. Information on setting up a user account.
Click on the link that reads "View & Respond To Company Reviews" (See Screenshot at right.)
Here you will see the latest 10 reviews listed. Right click and copy email address on the orange customer name. See example below. Or left click on the name to open your default email client with the email address already filled in.
