Note: There is no "one size fits all" redirect. Below are general guidelines. 

Art19 does not have a user interface from which you can setup a 301 redirect. Therefore, to migrate your feed, email Art19 at support@art19.com asking them to setup a 301 redirect from your Art19 RSS feed to your Megaphone RSS feed. Please only do this after confirming with the Megaphone team that the podcast(s) are ready for a redirect to be put into place.

Use this article for information on how to find your RSS feed in Megaphone. Double-check that the Megaphone feed is correct and working properly (you can test by opening the feed in a new tab).