You can either pay to sit in stands in La Ronde (local amusement park) and watch the fireworks rather closely, or you can do as thousands do and congregate around where the Jacques Cartier bridge meets island of Montreal to watch for free.

www.internationaldesfeuxloto-quebec.com/en/

On various nights, with different themes by different countries. Great views from the Old Port, even better from The Jaques Cartier Bridge