The first, and I suppose seemingly easiest claim and means to justify your place in the startup world, as someone who has no experience, is to call yourself a product person.
But that claim generally comes with a fundamental misunderstanding of what it means to do product. It is not code for a person who doesn't really know how to do anything but thinks he can boss engineers around. It doesn't refer to marketing guys who had an idea. Understanding what it means to drive a product means understanding the full scope of the vision of your company. It means understanding your engineering team, their capabilities, and their priorities. It means understanding what your next move is, and what your 6th move is from every angle.
Aaron also proposes a development plan for people who want to become product guys in reality as well as in title, which involves both practicing the craft and reading some product development classics.