Installing compact search in the main menu?

Please tell me how to install compact Search in the main menu WordPress, just as is done in the themes: Avada, Vantage, Twenty Fourteen. Or plugin UberMenu. In the themes Avada I like most. Site made on the themes of Avada: http://algolux.com/news/ If I understand correctly, there is a picture when you click on that appears below the search box. On the Internet, a little write about traveling search forms, but they require space. as the overlap menu. And add that I fixity when scrolling menu and the like to search form is also fixed. Sorry for my bad English. Thanks for the answers.