Were you able to successfully test serial connectivity to the device?
You’re going to need a USB cable to plug into your machine, one capable of data. If you’re using a Microsoft Windows computer, it’s probably best that you use the Web flasher utility. But if you’re set on using the commandline interface, it’s easiest to use from a Linux computer. You’ll probably have the easiest time using Ubuntu, but other distros should work. The initial setup documentation is pretty good, but it assumes you already know how to install packages and setup a Python virtual environment.
If you’re using Windows, try using the tutorial to get connected.