how I can create a car play application ?

To create a CarPlay application, you can leverage the next generation of CarPlay architecture and design system introduced by Apple. Here are some key steps and considerations:

Automaker Apps: These apps run on iPhone and allow you to create rich and custom UI experiences. You can use the full power of iOS to design interfaces that are highly visual and specialized for your vehicles. This includes custom settings, alerts, and notifications.
Customization: You have the flexibility to define everything in your app, from settings types, labels, icons, and functionality to the structure and order of the UI elements. The automaker settings API allows for this level of customization.
Vehicle State Protocol: This protocol helps configure the UI to adapt to the feature set of your car. It allows you to add or remove UI elements based on the vehicle's state, ensuring that the interface matches the specific features available in different models or configurations.
Design System: The next generation of CarPlay's design system offers a deeply customizable and integrated experience. It includes a flexible layout system, dynamic content, and the ability to theme backgrounds and colors across driver displays.
Technical Documentation and MFI Program: For more technical details and access to resources, you should enroll in the Apple MFI program, which provides documentation and support for developing CarPlay applications.

For a detailed walkthrough on how to enable custom features in CarPlay, you can refer to the session Meet the next generation of CarPlay architecture (21:19).