AA is now a built-in part of Android 10. It is installed by default with the operating system. In Android 9 in prior version, AA had to be installed from the store.
You can start it manually to use it on phone's screen or it will be activated automatically on your car's infotainment display (if supported) when you connect your phone to your car's usb port or wirelessly (works only on newer cars with wifi support for AA).