iTunes Internet Radio is no longer accepting new submissions or updates for stations. Unfortunately, this means that if you're not already listed on the iTunes Internet Radio directory, then you won't be able to submit your station to it.
iTunes Aren't Accepting New Stations?
Unfortunately, no. The official page for signing up for the service shows the following message:
Thank you for your interest in iTunes Internet Radio. We are not accepting new submissions or modifications.
I'm on iTunes, But Need to Make a Change
iTunes Internet Radio is also not accepting modifications to existing stations listed on the directory. This means if any details have changed, such as your station name, streaming link or otherwise, you won't be able to update it.
iTunes Internet Radio Alternatives
Although iTunes Radio is no more, there are alternatives. Streema, Internet-Radio, and many more are home to thousands of stations and plenty of listeners. So the more you're on, the more chances you'll get discovered.