Your site lives at yourevent.livejudgesite.com. The Site Address card in Site Publishing shows the address you have and checks any new one as you type it, so you know before you commit whether it is available.
Changing it
Changing the address moves your site immediately. The old address stops working the moment you confirm, so update any link you have already shared, on your own site, in email, and on social. Your LiveJudge connection follows the move on its own, so nothing has to be repointed there.
The one-year term
The address is included with your event for one year, and Site Publishing prints the exact date it runs through. After that the public address shows an archived notice instead of the site. Your content is not thrown away: contact LiveJudge to restore it.