Add a style css file for custom styling

Hi, very usefull utility and thanks for it.
As I titled, could be possible to add a style .css file to the module?

I would do it my self but do not know where to begin:

Maybe putting this some where in Worldclock.module file?

drupal_add_css(drupal_get_path('module', 'worldclock') . '/worldclock.css');

Cheers