I have a bunch of MP3 files that I want to treat as a podcast, so I can pause and resume without losing my spot. How do you set up folder structures and other necessary files in Windows Phone 8.1 to achieve this?
In oder to get podcasts into your podcast app you actually have to subscribe to one, either by searching our by entering a feed. You still can listen to the mp3s though the music app.
It might be easier though to try one of the audio book apps from the store - I think those offer the functionality you're looking for.
What is your end goal? Can Playlists suffice your scenario? Learn how to create a playlist from here - http://webcazine.com/4443/how-to-create-playlists-for-windows-phone-8-on-your-windows-pc/