I have just finished my first manuscript
"You wouldn't even know a diamond if you held it in your hand. The things you think are precious I can't understand"  Steely Dan
You write your story the best you can, edit it the best you can, then you look for a publisher or you publish your book yourself. Simple. Hundreds of authors do it every single day! Whether they actually sell anything at all is a completely different matter. As harsh as it sounds: if you can't sell your book to a publisher you might have a hard time selling it to your neighbour as well.
What makes you a writer is your unshakable believe that you have a story worth telling. Writing is the easy part, getting your book out to readers is what you should concentrate on.