[Plugin: FeedWordPress] Display enclosures

I believe this should work:

Within the feed’s Posts section, go down to the Custom Post Settings. Fill in whatever key value you want (e.g. mp3_url) and $(enclosure/@url) for the value. There is a short explanation of how this works just below the input fields.

For more on how to use these Custom Fields: https://codex.www.ads-software.com/Custom_Fields

– J. J. https://zepfanman.com

Try the code in this article. It worked for many people.
https://www.mycuteblog.com/wordpress/feedwordpress-displaying-attached-images/