An ebook is just a regular book, but on the computer. Any published book is at some point on a computer anyways. So basically you just write a book, and then advertise it. Just pick something to write about, open Word, and start typing.
You would also have to turn it into a PDF for people to download, set up a simple website and some way to get the ebook to someone once they order it. And of course you have to make people aware of the book so they know it exists.
This is not true. You do not need to turn it into a PDF. Granted this will help prevent someone else from claiming it as their own work, however that can still be done to a PDF anyways, so that doesn't make that much of a difference.