Hi there. The “New Feed URL” is intended to be a redirection of the existing feed URL (which you can view from the “View Feed” link at the top of that page) to a new location. You’d use this only if you were moving your website or your podcast RSS feed to a new location. An example of this would be you using a new domain for your show, or moving your RSS feed to a feed based on a hosting platform. But you don’t typically use this unless you’re moving the feed somewhere else.
To populate the feed normally you’d just want to fill in the Feed Details (Title, Description, Categories, cover image, etc.) and then Save those details. Then when you publish an episode to that Feed it will appear there.
Hope that helps, and if there’s anything else we can do just let us know.