Take a look at you navbar template, you'll see it's unordered list, you add different list items and that's pretty much it. Depends how exactly you want yours to look like, but you can take a look at the source of this one on DragonByte's.
I have sort of got this mod for the second navbar working on my site, but it always shows as selected / highlighted that's the only thing i cant work out, so if anybody knows how to fix it, help would be greatly appreciated..