"Well, that's all well and good, but how do we get my book into Walmart? They would sell a million copies of my book!"
I then explained that marketing a book is like rolling a snowball down a hill. When it first starts rolling, it is a small snowball. As it continues to roll down the hill, it gradually gets larger and larger. By the time it reaches the bottom of the hill, it is significantly bigger than it was when it started.
When a new, unknown author first becomes published, their book is the small snowball. It may go unnoticed at first, but with persistent promotion it will continue to grow. It may not grow as fast as the author wants it to, but in order to keep the sales and exposure going, the author and publisher must continue to keep pushing it down the hill. If the author stops promoting their work, what happens? The snowball isn't going to get any larger, and neither will the book sales.
Many authors want to begin at the top of the hill with the big snowball, but they only have a big snowball if they have a large platform from which to launch their book. Is the author famous? Are they well-known in their state, region or even across the country? Do they have a large following in their life or profession? If not, then they are starting with a small snowball.
You may have heard of the book "The Girls With the Dragon Tattoo" by Stieg Larsson. It's a book that has been made into a movie, which is now playing in theaters. The book wasn't published until after the author had died, and it was released in Sweden, Larsson's home country. Nobody outside of Sweden had heard of Larsson prior to his book being published, but it won an award and was well-received in his home country. A publisher in Great Britain took a chance on the book and translated it into English, renaming it from the original title, "Men Who Hate Women" to "The Girl With the Dragon Tattoo." The book didn't sell.
The British publisher resorted to giving away copies; leaving them in public places like bus stops where people would find and read them. Like a snowball, word of mouth grew until book sales picked up and "The Girl With the Dragon Tattoo" became a success. Eight years after it was published, the book is now a Hollywood movie.
That is an extreme example of a small snowball rolling down the hill and becoming something very big. Not every author will have this kind of success, but the journey will almost always begin with a small snowball. If you keep pushing it, it will become something bigger. You just have to keep pushing.