It's a little confusing, but if you go on the front page and go to the "supported stories," the first few chapters are free, but you have to use coins (which cost real cash) to read the rest of the book, or pay a few to read a single chapter.
I'm also pretty sure that this was kind of exclusive, as I think that only a certain amount of writers got this. It's still in beta, so that's probably why only a select group of writers were given the beta.
And about your question: I believe that paying for the stories is how you support other authors. I might be wrong, though, so you might want to ask around a little more if you want a more verified opinion.