After you start the judging period, your judges will receive invitations to start judging and you can check on their progress. You can view this progress on the Judging/Voting tab on your dashboard. See the Starting the judging period and How to judge an online hackathon articles for details.
The dashboard shows you which judges have started judging and their scores. If the judging deadline is approaching and certain judges have not made any progress, you may want to send them a reminder.