The first step is drafting the target audience and writing the elevator pitch that describes the book.
The second step usually involves making an author brand via website, podcast and blog tours, reaching out to book reviewers, using Amazon, Facebook and Instagram advertisements. In short, all the activities that will sell the book in the short term.
The third step is selling a book for a lifetime via using Q/A platforms around the globe like Quora and making an e-learning course or designing a movie script.