The Gecko theme after the installation has a search function in the header. In the standard configuration, this is a feature that allows you to search for WordPress content. You can enable or disable it (on desktop and/or on mobile) using the settings available in the Gecko Customizer. To get to them go to WP Admin -> Gecko -> Gecko Customizer -> Theme -> Header -> Header Search section.

If you are an Ultimate Bundle subscriber, you can expand its capabilities by enabling the New Search feature available through the Early Access plugin (PeepSo -> Config -> Early Access). Next:

1. Create a blank page with the peepso_search shortcode by going to WP Admin -> Pages -> Add new (shortcode should be in square brackets)
2. Update the navigation settings by assigning the newly created search page in WP Admin -> PeepSo -> Config -> Navigation
3. Go to WP Admin -> Appearance -> Widgets and place the PeepSo Search (Early Access) widget in the Header (Search) section
4. Customize the search settings in WP Admin -> PeepSo -> Config -> Search

IMPORTANT: This feature is in BETA version.