Prerequisites: Google Account—that's it!
Instructions: Go to colab.research.google.com and log into your Google account using the blue Sign In button in the top right corner.
After you've signed in, a new window will pop up showing you all of the Colab notebooks that are associated with your account (if this is your first time using Colab, there will only be "Welcome To Colaboratory" in there). There is a New Notebook link in the bottom right of this window.
Click that, and you'll be greeted by a fresh notebook to experiment with, and you're ready to engage in the workshop!