Creating a menu with the built-in WP menu that looks just like the one created in ATA

Maybe I haven't found a thread about this because it's so obvious. Still, I'm stumped, and I need help.

I like the menu I created using Atahualpa before the WP menu interface came along.

I'd like to switch to using Wordpress menus, but I want to style it so that it looks like the current one. Where do you customize the look of the WP menu bar?

Thanks, Lila