These options are located in the Theme Options > Header > Desktop Header tab. Then go to the Desktop Header Layout section.

Desktop Header Layout options control the general layout of the desktop header on your site. (Fig. 1)  (Fig. 3)

Desktop Header Layout options Screenshot
Fig. 1. Desktop Header Layout options Screenshot.

 

Desktop Header Layout – Illustrated as AControls the layout version of the desktop header. Sonnet offers a range of 4 customizable header layout versions to suit your site’s needs. (Fig. 2)

4 customizable header layout versions.
Fig. 2. 4 customizable header layout versions.

 

100% Desktop Header Width – Illustrated as BTurn on to have the header area display at 100% width according to the screen width. If the site layout is set to boxed (See Primary Layout), the 100% desktop header width is controlled by the set site width. Turn off to follow site width.
This option is Not available if the Desktop Header Layout is set to the Desktop Header version 4 (Sidebar Header).

Sticky Header On Desktop – Illustrated as CTurn on to enable the sticky header when scrolling on Desktop. Sticky header is a term used to describe a fixed header on a web page that remains visible and in the same screen top position as the user scrolls down and moves about a site.
This option is Not available if the Desktop Header Layout is set to the Desktop Header version 4 (Sidebar Header).

Sidebar Header Width option Screenshot
Fig. 3. Sidebar Header Width option Screenshot.

 

Sidebar Header Width – Illustrated as DControls the width of Sidebar Header.
This option is available Only if the Desktop Header Layout is set to the Desktop Header version 4 (Sidebar Header).