Install a text editor; I recommend Atom or TextWrangler or Kate. Configure your editor to indent using spaces only (no tabs!), with either 2 or 4 spaces per indent level.
On Windows, Notepad is not a sufficient text editor for this class. Install Notepadd++, or, better yet, Atom.
Important note: Atom, like many other text editors, is free (as in beer and as in speech). However, not all text editors are. If you use a commercial text editor (one you have to pay for), make sure that you pay for it. Of particular note is Sublime: this popular editor is commercial, and you have to pay for it if you want to use it for an extended period of time. I'm pretty particular about this sort of stuff, and I will check on it in class.
Hand-in: Type some stuff into your editor and take a screenshot.