Want your gallery of images or videos to overlay your entire site? Here's how:
1. In the Admin launch the MEDIA LIBRARY and double click the media item you want to have this behavior.
2. Under SETTINGS scroll to Display Behavior and choose Overlay.
3. The Overlay has an icon that you click to close it (an X). To adjust the settings for the Close Icon open the DESIGNS panel and launch the Desktop Layout. Under IMAGES & VIDEO if you scroll down you will find Media Overlay Options: