In order to set a redirect from Podcast.co (PodCo) to ART19, please reach out to PodCo support directly (their support is available via their Chat Widget in your PodCo dashboard or by emailing help@podcast.co) and requesting a 301 redirect and providing them with your new ART19 RSS Feed URL.
For more information on migrating off PodCo reference their help center article on leaving their hosting platform here.