Two ways to publish a book. Have someone do it for you, or publish it yourself.
Have someone do it for you:
Write a book proposal which includes:
An outline, 3 sample chapters, a marketing plan, and a query. Send it to agents using the Literary Agents Guide. Wait 3-6 months for a response. If someone agrees to represent you, they will shop your proposal around. If a publisher offers you a deal, then you will write the book, send it in for editing, and production, you'll get a small advance against royalties, and then you'll wait up to a year to see your book on the shelf. You'll make between 35 and 80 cents per copy sold, and you may never see a dime. Likely you'll end up taking your publisher to court to get your money. And they will drop your book as soon as the rush is over. You'll spend countless hours and money marketing and promoting your book and your publisher will reap the reward.
You can self publish. Get Dan Poynter's Book "Self-Publishing Guide", write your book, have it edited and produced, get it printed, and start selling it! Get a distributor, sell it on Amazon and Barnes and Noble's websites. You'll make between $2 and $15 per sale, and your book can sell for years or as long as YOU want it to.
Can you tell I'm biased? Self publishing has been very very good to me.