Submitting to TuneIn requires you to submit an enquiry via their website.
Go to TuneIn’s podcasting page
Click Publish a Podcast
Note: TuneIn does not seem to like long feed URLs. Please use a link shortener like bit.ly to shorten your RSS URL first and submit the shortened URL.
3. A new page will open that will allow you to lodge a Support ticket
NOTE: The page used to be a contact form, but TuneIn appear to have updated their site.
4. Submit from what appears on the page and follow the steps they send you.