Hi Andrew,

Please before you continue with further steps consider reading the article we wrote about How to Add Custom CSS to your site, then please paste the code below in Custom CSS Section.

header.main-header .logo-and-menu-container {
    display: flex;
}
header.main-header .logo-and-menu-container .logo-column{
    display: flex;
    margin: 0 auto;
    width: 270px; /* this depends on logo width */
}
header.main-header .logo-and-menu-container .menu-column, 
header.main-header .logo-and-menu-container .mobile-menu-column,
.main-header.menu-type-standard-menu .standard-menu-container{
    -webkit-box-pack: center;
    -ms-flex-pack: center;
    justify-content: center;
    display: flex;
}

Thank you.