By default, you can find this setting under Customize => Layout => Page Header. This setting will help you enable the header cover image for all pages and posts.
But in case you would add the individual page or post featured image is header cover and show page title/excerpt on that area so please do the following steps here:
- Go to your individual page or post.
- Find the Customify Setting box.
- Under Page Header Display setting, choose Cover.
- Add a featured image.
- You’re done.
To add the page/post excerpt, please refer to this article: How to add the page excerpt content