You don't need to add anything — every Podpage automatically includes the RSS tag in its HTML. Some platforms require this tag to verify that your website is the official home of your podcast, and Podpage takes care of it for you.
Here's what the tag looks like:
The tag is embedded on every page of your Podpage website with your podcast's name and RSS feed URL filled in automatically. Any platform that checks for it — like Spotify for Creators (formerly Anchor) — will recognize your Podpage as your podcast's official website.