I am working for a company developing car audio system. I would like to know where and how I can get Carplay SDK or Engine.
Carplay SDK or engine
If you're asking about the CP API as a dev, see: https://developer.apple.com/carplay/
From that link if asking about making hardware: "If you’re interested in developing a CarPlay system, you need to be an MFi license. Learn more about the MFi Program"