Moderator/Assistant account is the same account as DJs but without 'DJ Can Stream Music' option. Click on the Create a DJ Account link from the left menu. This way, you can create Moderator/Assistant accounts by setting DJ Can Stream Music permission to 'no' and select other desired permissions. The moderator/assistant can login to DJ Panel(2080) and use given permitted features like starting/stopping radio or AutoDJ and some other on air features. They cannot stream music as the DJ Can Stream Music permission is set to no for this type of account.
Be careful on the permissions, you don't want someone start/stop your radio in the middle of a show or scam your radio.