Fill out the iTunes Content Provider Application. The entire application process is online. Some of the details requested include basic contact information, whether you are an independent artist or group, independent music label or music distributor, and for which global territories you own distribution rights to your music.
Wait for a response from iTunes. They might accept it immediately and respond with login and management details about your account or they might respond with requests for follow up information to verify your ownership rights over the content you plan to supply.
Login to your iTunes content provider account and read through all of the literature provided about managing your account. From your account manager page you will be able to create releases. Releases are usually in the form of singles, EPs (Extended Plays, 3-4 songs) or LPs (Long Plays, six songs or more). In addition to setting up your releases, you can upload artwork and promotional text that will help your releases gain attention.
Sign up with a third-party music distributor that feeds content to iTunes. The benefit here is that distributors will get your music into other music outlets in addition to iTunes. The drawback is that the distributor will keep a percentage of your total royalties, albeit a small one, and some distributors are very selective about which artists they will carry.
Login into your distributor account, create a release and upload the music, artwork and promotional text for the release.
Set the release date for your release. Since most distributors offer the ability to release your music through various online music stores, you can choose different dates for each store if you choose to. This allows you to make your music exclusively available through iTunes for a limited time before releasing it to other stores. This strategy can help entice iTunes to feature your release since it will be exclusive, but there are no guarantees.