Exercise https://jsbin.com/tigikaw/edit?html,output
That's it, no lengthy text on the history of VR, no complicated instructions, follow the link, spend the time you want on it, explore the documentation if you feel like.
You don't see what you have done in your phone? Check the steps :
Make sure you are comfortable with JSBin to maximize your screen real estate, be able to save what matters, have preview on the phone, etc.
Once you think you are done discuss what you have learned, what made sense, what did not, what you think is missing for you to go further and explore your ideas.
What do you need to know now to make a proper VR experience?