Write your book and have it edited by a professional editor.
Choose a self-publishing company to work with. Read about multiple companies and decide what will work best with your budget, your goals for your book, and the available options for production, distribution and marketing.
Format your book according to the specifications needed by the publisher. Check that your page margins are correct. Upload your file.
Design a cover for your book using photo software such as Adobe Photoshop or Adobe Illustrator. Upload the cover design.
Purchase your publishing package. Be sure you get an ISBN so you can sell your book at major retailers in-store and online. Order a copy for proofing.
Proof the hard copy once you receive it to ensure everything is correct. Once it's right, order as many copies as you personally need. Develop a marketing plan and get those book sales rolling in.