Running Open EdX locally for the first time

I’ve gone through the local install process of Tutor on my Mac and everything seems to be set up properly, but I’m unclear on how to actually launch Open EdX in my browser. I did:
tutor dev runserver cms
and got the message:
The cms service will be available at http://studio.local.overhang.io:8001
but then
ERROR: pull access denied for overhangio/openedx-dev, repository does not exist or may require 'docker login': denied: requested access to the resource is denied
I don’t quite follow, as Docker is installed and running on my machine. I’m completely new to Tutor, to Open EdX, and to Docker, so any assistance is appreciated.

You have to first build the dev image as it is not available to pull/download.
You do this by running

tutor images build openedx-dev