A Referee Assignor account is independent, allowing an assignor to work for multiple leagues and tournaments. An assignor has to open their own account and then link it to your event.
Login to your Assignor account and go to Referee Tab then Events in the Black Menu bar, and search events in the Grey Menu bar.
Search for the event then click on the event name.
When you are on the event click the register as assignor button.
The League/Tournament Director:
Go to officials and then assignors and hit the approve button.