Can you please share a link to your website? So we can see your current setup.
Usually, it should be under Elementor templates pages.
Edit: We saw a link in your other ticket. We can see that it is built with Elementor, so it should be under Templates > Saved Templates > Header. You also should be able to edit it from the home page when hovering on the Elementor (at the top bar) and selecting Header template.