How to keep the size of the screen fixed when playing in a bigger monitor

Hello, guys!!! I'm having a problem with a game for PC and Mac. If the player opens my game on a wider screen, you can see sections of the scene that shouldn't be presented. This is the error. My game is a 16:9, but I saw cases where the proportion can be 32:9, so, I need to restrict this size to 16:9. What should I do? Thanks.