The simple answer to this question is, you do.
The company may try to tell you that the union is run by outsiders, not from around here, but that just isn’t the truth. It is you who will elect a negotiating committee to bargain your first collective bargaining agreement. It is you who will vote to accept or reject that contract. And it is you who will elect your local leadership.
The union is made up of all the workers in your plant, and is run by the members in your plant. By coming to meetings and staying active, you will have a big say in how your Local union operates.