If you're importing a podcast from Simplecast, you'll want to follow the following steps to set up a feed redirect:
Log in to Simplecast.
Click on the podcast that you wish to add the redirect to.
Visit the Podcast Settings tab on the left.
Under Advanced Options, fill the "RSS Feed Redirect" field with your Pinecast RSS feed URL (you can find this on your Pinecast podcast dashboard).
Click Save Changes.