You can Google and find a bunch of them that already exist specifically for Genesis, but if you look in your functions file you’ll see something like this –
wp_enqueue_style( 'google-fonts', '//fonts.googleapis.com/css?family=Open+Sans:300,400,600', array(), CHILD_THEME_VERSION );
Replace Open+Sans
with the font you’ve selected from the Google Font page. You can also swap out the weights if you want to.