Delete an Episode or a Feed
To manually delete a feed, right-click on it in the tree under Podcasts and select Delete.
When a feed is deleted, all previously downloaded episodes become "orphaned" and are eligible to be deleted according to the Keep Orphan Episodes setting in Tools > Options > Podcast. If you then resubscribe to the feed, any existing orphaned episodes will be reattached to the feed.
To manually delete an episode, select its feed in the tree under Podcasts or use the search function, and when it displays in the content pane, right-click on it select Delete. That episodes status changes to "deleted" and will not be automatically downloaded again.