Documentation
Select “Media File” at “Link to” when creating a gallery.
If the plugin is active, the images are now open in the lightbox.
The plugin requires PHP 5.3.2 or newer.
This plugin uses Lightbox2 from Lokesh Dhakar, fancyBox3 from Jānis Skarnelis, Colorbox from Jack Moore and Justified Gallery from Miro Mannino.