This snippet is used in the following knowledge base article – https://kb.wpbeaverbuilder.com/article/291-center-the-nav-menu-with-nav-bottom-layout
.fl-page-nav-bottom {
text-align: center;
}
.fl-page-nav-bottom ul.nav {
float: none;
}
.fl-page-nav-bottom ul.nav > li {
display: inline-block;
float: none;
}
.fl-page-nav-bottom ul.sub-menu {
text-align: left;
}