After you are done writing your prereview, you can click on "Document" (top left), "Publish" so that your preprint review will be public and will be assigned a DOI that you can use to advertise your review on social media, email to the authors, and post on the comment session of in the server where you got the preprint for your JC. Additionally with a DOI, your preprint review will be citable!
If you got this far, GREAT JOB! Thank you for supporting open science and helping science move forward faster!