To replace the media file (audio) of a single episode you can follow these instructions:
1. Log in to your RSS.com account https://dashboard.rss.com/auth/sign-in/
2. Click on the 3 dots within the box of the episode to edit:
3. Next click on "Edit"
4. Scroll to the bottom of the screen, and click on the X. This will remove the current audio and allow you to replace it with another.