Go to a distribution company like CD Baby (cdbaby.com) or TuneCore (tunecore.com).
Click on the link to register for a new account.
Enter your personal information, submit your CD artwork and music and pay the start-up/annual fee. CD Baby and Tunecore will make your CD available for physical and/or digital purchase.
Set up an artist website if you haven't done so already. Hire a developer to build a store on your website, if you can't do it yourself, and connect it with your bank account.
Promote your CD on social networking sites like Facebook and MySpace, music forums and music websites like PureVolume and GarageBand.