Expansive spacing between navigation links

Hi there!

My client would like for their website to mimic a poster I designed for them (first image). I've figured out how to get the logo to take up the full width, but I'm having a hard time finding the right code to get the navigation links to be equally spread along the width similar to the "75+ vendors..." text on the poster.

Website is farmerandtheflea.co

Hope there's an answer out there somewhere! 

Thanks! 🙂

@tuanphan You've always been so helpful! Any suggestions here? TIA 🙂

Add this to Design > Custom CSS

nav.header-nav-list {
    width: 100% !important;
    justify-content: space-between !important;
}