The incident plot point causes your hero to make a choice. (We will cover the choice next time.) Something needs to happen for them to want to change their circumstances or their world. And the bigger the better.
Let’s say your hero lives on a beautiful, calm planet where they are enjoying the peace of their world. The incident could be an alien attack! Or all the water becomes contaminated by something bubbling up from the planet’s core! Or big corporations dump hazardous chemicals into the water system. Everyone is freaking out!
Making your hero’s world chaotic is an excellent choice.
But you can also instigate change in their lives in a more subtle way. Maybe a relative dies and leaves them vast amounts of money, or a run-down house. Maybe your hero was being supported by someone, and their death causes them to lose their home, their job...
Whatever you choose, it should be something that is beyond your hero’s control. It must be an outside force that flips their world.