If you're importing a podcast from Anchor.fm, want to follow the instructions from their support site:
Log into your Anchor account on the web
Click Settings in the top right of your screen
Scroll down to advance settings and insert your new Pinecast feed URL into the box provided for Redirect URL. You can find your feed URL under the "Important Links" section on your Pinecast podcast dashboard, or at the top of the Distribution tab.
Click redirect my podcast