A sticky header is a menu or navigation bar that stays at the top of the page no matter where you scroll. In other words, a “fixed” header. It will allow quick access to the menu from any part of the page.
It is a premium feature available with Suki Pro. You can activate the module from Appearance > Suki > Sticky Header
You can find the settings under Appearance > Customize > Header > Sticky Header. This setting is global default setting for sticky header.
If you want to override sticky header global default setting on each different page type (posts archive page, single post page, search or 404 page), please go to page settings. You can also override the sticky header setting (enable/disable sticky header) on each post/page using page settings metabox in post/page editor.