How to replace OpenSans font?

wp_register_style('OpenSans', 'http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic');
wp_enqueue_style( 'OpenSans');

You can use fonts from google – http://www.google.com/webfonts

If you want to replace Open Sans for Yanone Kaffeesatz font then replace

wp_register_style('OpenSans', 'http://fonts.googleapis.com/css?family=Open+Sans:400,700,400italic');
wp_enqueue_style( 'OpenSans');

for

wp_register_style('Yanone', 'http://fonts.googleapis.com/css?family=Yanone+Kaffeesatz');
wp_enqueue_style( 'Yanone');

Now open style.css and replace “Open Sans” for “Yanone Kaffeesatz”.