At the time of this guide, there is no version of the Mu editor (Adafruit's preferred CircuitPython editor/REPL) for Chromebook.
Instead of Mu, two programs will be used. One is a text editor and the other is a terminal program to see program output and error messages.
You will need one of each type of app from the Chrome web store. Apps can cost money or they can be free. We have selected two free, compatible programs, you are free to chose other programs:
Once installed, you can launch the programs from their Chrome page or via the Chromebook Start circle.
See the next couple pages on using these apps for CircuitPython work on your Chromebook.
The pages refer to the following other Adafruit CircuitPython tutorial: