This feature- Reviewer Locator (helps to find reviewers)- is only accessible to journals that are taking part in the Publons pilot.
Alternatively, you can use the direct link to the Web of Science Reviewer Locator.
To find more information on how to use the Reviewer locator you can check the FAQ of Publons.
Monique is the Application Manager of Open Journal Systems (OJS), Open Monograph Press (OMP) and of the WordPress websites at tudl.tudelft.nl