The posts can only have the modern/full-height header style (example: https://codeless.co/specular/default/?p=33) or Centered style.
Select the “Normal” or “Full Screen Post” header style in post’s Blog Post Style: https://ibb.co/ZW95hHr
If you select the normal style, then scroll up to the General section. Go to General Settings > Page Header Options > Page header style, select ‘Centered‘. Screenshot: https://ibb.co/n0WMGt5
To further customize it, go to theme’s General Options > Header Options > Default Page Header, add an image for the background here and set the header height.
