Connect the AutoPi dongle to your car's ODB-II port. This port can be found beneath the steering wheel, somewhere on the driver's side.
There are several versions of the AutoPi dongle available. A few of them come with a Raspberry Pi Zero preinstalled, but there's also a cheaper version where you "bring your own Pi". The DIY version should be enough, especially if you want to use the larger, more powerful Raspberry Pi 3.
By default, the AutoPi has no graphical user interface. We'll need to install one.
Install the interface
The graphical interface is technically a website that needs to run in Chromium's Kiosk mode. You can learn how to install the interface using this guide.
Configure the interface
Once you've installed the interface and logged in, you'll be able to configure it.
You can add tons of other customizations to your Raspberry Pi car computer, including: