There are 2 global options related to header image.

Select header type to be global (all pages, all posts, all properties, all agents, all taxonomies, all archives and categories)

and Enable parallax for all header media with image or video

If you wish to use header image only for a specific page / post / property / agent / use this option and you have more images options

If you use Image or Video in header you can enable this option to detect user location on homepage

Demo – https://london.wpresidence.net/

Help: how to add image in header – http://help.wpresidence.net/article/1-30-3-header-image-and-parallax-effe/

Help: how to add video in header – http://help.wpresidence.net/article/1-30-3-video-header-option-for-each-page-post/

Parallax effect applies if your image height is larger than 300px