How do I begin a business?

Hi fellow Fluther(ers)! I’d like to begin a new business venture with a friend of mine. I am going to keep our business undisclosed for now as I do not want to disclose something that may hurt my business venture success. I’m new to all of this (and quite young, if I may add). It’s never too late or early to begin something new and this is my chance. I do not know where to get started. I have an idea of what I’d like to sell and am working on the prototype stages. From there, I have no idea how to proceed. I would greatly appreciate your insight on this matter.