Here a video tutorial how use this plugin for generated featured image from youtube video embedded in your post

    (AUTO) FEATURED IMAGE FROM YOUTUBE VIDEO

    The plugin detects if there is an embedded YouTube video in a WordPress post. If a video is present, it will extract the image from the video and use it as the featured image for the post.

    Use YouTube Image Setting

    For this functionality to work, the 'Use YouTube Image' option must be enabled in the plugin's settings under the 'Image' tab.