Step 1: Navigate to Appearance from your admin dashboard then click Customize. Next, hit Header. You can see a list of available header styles.
Step 2: Click on the header style you want to customize.
Step 3: In each Header Style, you can customize Header Components, Header Navigation...
Note: Maybe you will not be able to see the changes you made because the page already had a priority settings in Page Options, then you can go to the page to check again.
Step 4: After customizing, do not forget to click Publish button to save your changes.