How to create a WordPress YouTube Playlist Gallery
1. In WonderPlugin Gallery, step 1, click the button "Add YouTube Playlist".
2. In the popup dialog, enter your YouTube API key and the playlist ID. You can also enter a value for the Maximum Results. If you don't enter a value, it will return 5 videos by default.
For how to apply for a YouTube API key and find the playlist ID, please view the tutorial: How to apply for a YouTube API key and find your YouTube playlist ID
3. Save and publish the gallery, copy the provided the shortcode to your page or post, the WordPress YouTube playlist gallery is ready to go.