Android Auto isn't yet in a lot of hands. And that's largely because you need a head unit from Pioneer, or you need to buy a new car which has Android Auto. Currently only Hyundai is selling cars with Android Auto - however they don't have the update for Android Auto just yet. We do expect Android Auto to make a big splash in the next few years though. And for those interested in buying the Pioneer AVH-4100NEX unit and installing it in their dash, here is how you set up Android Auto.
First you're going to need to connect via Bluetooth. You only have to do this once, as most of you know, Bluetooth will automatically connect as long as Bluetooth is on, on the device. However if you switch devices or do a factory reset, you will need to repair them. You also need to be sure the Android Auto app is installed on your smartphone. Now plug your device into the microUSB cord that's plugged into the car or head unit. Sometimes Android Auto will think you're moving, so it'll come up with a big red screen that says "STOP" and "Android Auto Auto setup will resume when the car is parked". Sometimes you might have to put on the parking break to get past this.
Now into the actual setup process. The first screen you'll see is a purple screen that is basically telling you that Android Auto is going to use Bluetooth and access to your notifications. Just hit Accept. Next up is apps. If you don't have Android Auto (which would be kinda hard since you're using that app right now), Google Maps, Google Search or Google Play Music, it will recommend you download them and sign in. In fact, if you don't, it'll ask if you are sure you don't want to sign in. Now it's going to download those Android Auto apps that are not already downloaded. Now the Android Auto app is going to ask for permission to use these apps when your phone is locked. Easy peasy. Finally, is the disclaimer telling you to watch the road not the display in the car. Just hit Accept and you should be all set.
If you have a Pioneer head unit (although this applies for Android Auto that's built into cars as well), you'll need to tap on the "Android Auto" app icon to open up Android Auto and use it in the car. Not hard, but it is something that you need to do. It's also worth mentioning that some devices take longer to hook up with Android Auto than others. For example, if I plug the LG G4 in, it takes a few seconds and Android Auto is up and running. However, with the Galaxy S6, it takes a bit longer, and sometimes I need to unplug and replug it back in to get it to pop up. So just something to be aware of.