Superstition is using the SugarCube format!
After choosing your story format, you should go and look for the documentary of it. This is SugarCube's:
https://www.motoslave.net/sugarcube/2/docs/
You will find information about the various macros / commands you can use. These vary between the various story formats.
Depending on your level of familiarity with coding, the language used can be a bit overwhelming at first or make complete sense from the get go. It is always useful to try the macros out yourself to see how they work.
If you choose SugarCube, you should also go and check out the amazing custom macros some dedicated people created, especially those by Chapel.
In terms of how to learn how to code a Twine project:
If you have a specific question, you can try to search it online to find a discussion on the old Twinery forum. There's also the subreddit r/twinegames where you can go to ask questions.
And of course the most valuable help at the start: Read the code of a few already completed stories. See how these authors set things up, what you would do differently and what you wouldn't have thought of. As the Twine project files are all saved as HTML files, you can open them in different programs like Notepad++ or Sublime once you've downloaded them.
I hope this helps a bit!