Welcome to the forum. Light up a portfire and join in the fun.
As for the question..... I'm sure you'll find answers in here somewhere.... have a search around or see what replies folk come up with. For my part, I got sort of head hunted by a professional display company. Other folk have asked display companies if they can come and help out as volunteers. Whilst still others have gone on one of the few training courses offered from time to time. Have a look in / keep an eye on the Recruitment section of our Professional forum area.