How do I have the first image in the post automatically be the featured image?

Please see the code below, it is a scroller with a post preview and image, but the posts only populate if they are featured. Because these posts are coming from RSS feeds, I need to put the images inside the posts as featured images manually. How can I correct this so its instant? It would be a BIG help!

[Code moderated as per the Forum Rules. Please use the pastebin]

Does the below link help?

http://www.wpbeginner.com/wp-themes/how-to-set-a-default-fallback-image-for-wordpress-post-thumbnails/