does anyone know how to center the navigation on this theme, I’ve tried everything I can think of.
If you have tried everything I guess you have already answered your question 
You might want to try code like this via Theme Options - Other - Custom CSS.
.nav.navbar-nav {
float: none;
margin: 0 auto;
max-width: 500px;
}
What it does is sets max-width, removes float and alights menu in the middle.
By default menu is set to full width which obviously means that you can’t center it since it already takes the entire width of its parent container.
There might be some problem with this example and this is only general idea how it can be done.