Apply by email or in person. Union wont look at you unless you have experience in a trade or some form of certification/schooling. Example being ticketed milright or electrician.
All training by union is done in private classrooms and in the field during your apprenticeship. You work an go to school at same time. Some days your working from 7am then at school till 10pm.
The industry is booming, lots of work. man power is needed. With the government getting involved in licensing, things are a bit of a mess right now.
Other option is to apply at non union companies and get experience in the trade an keep applying to union till they give you a interview.