A search page lets users search the whole site for the most relevant content based on their search query.
Add a page
Set the template to search
Give the page a name like search
No content is needed
Set the date to a date really far in the past (so the search page does not show on the search page as it will be shown first as its just been created)
Set the read settings to search
Add the search the page to the menu
Show the CSS classes
Add the Search CSS Class
You will now see the search icon in the menu