How to change the header and edit other Single Shop Product page settings?
On Appearance > Customize > Shop panel there is a Settings Page Slug field. This field should contain the slug of the page which serves as a template for all products items. All single pages of products will inherit settings and shortcodes of the page referenced via this field.
In order to change elements on single page of the product item, please locate the page with the slug entered in Settings Page Slug field and edit it.
For more info and detailed instructions please refer to our Online Theme Documentation.