This is a premium feature available with Bstone Pro Addon plugin. To use these Pro features, you need to have the Bstone theme along with the Bstone Pro Addon installed on your website.

The sticky header will fix the header in the top portion of your webpage when a user scrolls the page. It will allow quick access to the menu from any part of the page.

You can find the settings under Appearance   Customize   Header Builder   Sticky Header.