I don’t see the Lato font anywhere in the this theme. The only font’s I see are Open Sans and Source Sans Pro.
If you don’t want to change the fonts in the CSS there are some Google Font plugins you can download and try. WordPress.org has quite a few free ones for download. I’d try any of those first to see if they work with the theme. I thought I saw a plugin made specifically for Genesis Themes, but can’t remember the name of it.