[development] Creating theme configuration options

Hi, I would like to add a few options in my Drupal theme that can be configured by the administraor such as twitter username, rss feed url and email subscripotion form code and so on. I understand configuraiton of a theme is done under Themes > Configure [next to the theme]. How do I add my own fields to that page for configuring the theme? Thanks in advance, Raj Sekharan