To associate a screenshot and add credits for a theme on the WordPress theme selection page, simply add a file named « screenshot.jpg » and place it at the root of the theme.
For the credits, just add the following code to the style.css file at the root of the theme and include the following header:
@charset "utf-8"; /* Theme Name: Le nom de mon theme Theme URI: http://ledomainedutheme.com/cequetuveux/ Author: partITech Author URI: http://www.partitech.com Version: 1.0 */