Post Not sure if Kindle Fire HDX 8.9 is rooted

I have a Kindle Fire HDX 8.9" Current Version:

I tried to root my kindle a few weeks back and got a bit confused. I can't tell If I have rooted my kindle succesfully.

Installed ADB (Windows states that driver is already installed)
Try to update device drivers, select kindle but no device drivers are avaliable to install.

I'm just really confused. I just want to learn how to root a kindle, install a custom ROM then be able to restore it to stock if I don't like it.

Can any one tell me if I have rooted my device or not?