There was no interview process to become a referee for USA hockey. You must enroll and pass an officiating class/seminar and written test. There is also an on ice skating portion that same day to work on positioning and skating fitness. It would be benficial to watch referee positioning in an NHL game and also look over the rules of professional ice hockey before the seminar because a lot of previous knowledge is expected. USA hockey sends you a rule book prior to the clinic which would be advantageous to read beforehand.
Take a course at a local rink which you can find online at USA Hockey, and take the required seminars. Then complete the modules and take the referee test to be certified. You then typically contact the rink assigner for the rink of your choosing. It is less of an interview and more of an offer of your services as the sport is hurting for referees. To find a rink assigner look online for a rink nearby and find their contact info.
There was no interview process in the district I refereed in. Once you are USA Hockey Referee certified, you should be able to register with your district's hockey program/ice rink and get set up to referee games.
There isn't really an interview process. Purchase a rule book and handbook and study them for the the tests. You need to attend a class session and take an open book test. if you are going for a level 3 or higher Referee position you will need to take a closed note test.