Press the blue button under the rearview mirror to get through to customer service for free. Then you can ask the other party how to use OnStar in detail (depending on your package, there will be different functions), and you can call customer service through official website.
The basic usage is very simple: press the blue button to connect to the general customer service and ask for services such as navigation and vehicle detection. Pressing the red button to connect to emergency customer service can help. The white key is a self-service voice key.