As I'm told, online publishing is a nightmare, especially getting paid. You really have to trust whoever is posting your work. Then there are the legal issues. Other than "fair usage" clauses and Copyrights, I admit, much of it I know nothing about. So you really want to find someone that does. Knowing, is the difference between selling your work, and giving it away. Many of my friends ended up giving years of work away, just because they "didn't know".
I'm guessing you're not a writer by profession, based on the fact you're asking us for advice. But just in case, I'll offer up two of my friends for you to get info from.
Trey Wickwire
Trey is a writer by profession. He and I ran into each other through Syfy.com's message board (never met in person). Although currently working on television projects, he is also published in comics. In my discussions with him, he has a great deal of experience and knowledge in the field and is very approachable.
Wil Tibbetts
Wil is NOT a writer by profession. He and I have been friends for many years, and he also is published. What he did might be what you are looking for:
Emily Reynolds Saga: Book One: Survival
Either or both can give you much better advice than I can. Hope this helps.