First off, don't call it a manga. I can't take a person seriously when they call it that, and I'm pretty sure publishers wouldn't either.
Second, study art. Study everything. Anatomy, composition, lighting, color theory, movement, dialogue, writing. Before you even start to develop a style, you're going to need to know how to realistically portray what you plan to draw. And if it even crosses your mind that you don't need to know anatomy BECAUSE YOU ARE MAKING A MANGO, then give up now, because you aren't even remotely ready.
Then, after you can draw and write convincing stories/dialogue, you can move on to the next part. Moar studying!!1!! Panel layout, drafting, word bubble placement, inking, coloring, action sequences, shading (either halftoning or some other method like crosshatching). Also, writing in a proper comic format. It'll look a bit like a screenplay.
Then, when you have THAT down, you can start planning your comic, starting with the plot. Then you write your script, draft out your panels and sketches, and finally ink and color. Along the way, of course, getting as much critique as you can. And not nice critique, either. People are going to tear your work apart. And even then, it's probably not going to be as harsh as an actual publisher will be.
Then, after all that hard work, you're going to need to contact a publisher. Whether or not they'll want a full volume or something else, you'll have to see. After that, it's up to the publisher you contact what happens.