No, you do not need to do a Judge training. There is a short tutorial that opens for Judges once they open their unique ballot.
Depending on your event, you may want to do a Judge training to explain to Judges how to interview Competitors, or what to look for in a Competitor, but that is at your discretion.
We recommend using a different event for your judge training than your actual event. Just click "Create New Event" at the top right to create a training event. You can even copy your event details by clicking "Copy Event" at the lower left after you click Create New Event and select the elements you want copied.
We recommend setting up a demo event for yourself to really see what it's going to be like! You can also check out the Judge Experience Video here.