File Uploads and Audiobooks
When you sign up for the Premium subscription ($10/year) you get the option to use File Uploads. This is an interesting feature but there’s almost no documentation on it anywhere, even within the app or on the website.
Once you get your premium subscription, you need to log in to the Overcast.fm website, then scroll past your Active Episodes, and under the list of Podcasts, click on a new podcast you’ll see there called Uploads. (You could also go to https://overcast.fm/uploads after logging in. )
There you can upload any audio file. (The site will prevent you from uploading other types of files.)