I'm crafty by nature, so the letters DIY never frighten me. But for others, it's a terrifying prospect to create a book from scratch and market it to the masses. The popularity of self-publishing has led to a wide availability of services geared toward indie authors. At some point, you may be tempted to hire someone to publish your book for you. I'm here to tell you not to do that.
The moment you begin writing out that idea which has taken root in your imagination, it stops being yours. After you write your manuscript and turn it into a book and share it with anyone, it will become something different. That book will never look to readers the same way it looks inside your head. You're the only one who will ever really understand that book, everything about why you wrote it and what it means.
That's why you're the best person to turn that manuscript into a book that others can read. Believe me, this is not going to feel like the most attractive option when you're in the thick of it -- but it still remains the best.
Look up self-publishing on Google, and you're going to be inundated with companies offering a wide variety of services for indie authors. You can hire someone to take care of every aspect of your book. It's possible to find an editor, pay for formatting and you can even purchase easy publishing. But I don't think you should do any of that. I think you should do it yourself.
Not just to save money, though at some point that should absolutely factor into the decision-making process. You're the only one who really understands your book, so you're really the only one who can bring it to life. You'll learn a lot more about your writing style (and bad habits) if you do your own editing. In fact, editing your work is more instructive than writing your work in many cases. You should read and re-read your own words and get to know who you are as a writer. This is the only way you will learn how to improve.
Once you get past the editing, the rest of the process really isn't that hard. I know a way to cheat on the formatting to make everything very simple, and once that's done it's really smooth sailing. Self-publishing is always something you should DIY, because no one will love your book the way you do. Save your money for marketing...because as an indie author, you're going to need it.