Creating a list of select options

[starapple2]

Not an issue but seeking info. Is their any guidance I can find on adding a select box with a list of options? I have an array of country codes and countries I'd like to present as a Country List generated by:

$countries = array(
  'gb' => 'Great Britain',
  'us' => 'United States',
  ...);

   foreach($countries as $code => $country):
        echo '<option value="'.$code.'">'.$country.'</option>'; 
    endforeach;

I've followed the instructions to display a Field Group choice, Country Select but need to know how to set the list of countries and offering the choices for the Return Value.

Thanks.