change the nav bar

i made two sites one with bueno and one with the bricks theme

https://royal-arubacarrental.com has the bueno theme
and
https://aruba-comfort-apartments.com has the Brickyard theme

on the brickyard theme the navbar sticks at the top when you scroll the page i really like this and want to change the navbar behaviour on the bueno theme also this way

doen anywone knows how to do this ?