Different featured images for different pages as Header images

www.computerland.lk I’m currently building this website. I am having an issue figuring out how to work with the featured image from page to page. I have a header image on the home page. I have selected 'Enable on Homepage/ Front Page' in the Customize->Header media section. I would like the page images to be different, but when I go to Pages>Featured image (in the lower right hand corner) and enter an image, it doesn’t show up in the concerned page.