The Theme Editor lets you modify the template files, the stylesheets and the JavaScript files of the theme you are currently using..
The file list is divided in three sections :
The yellow bullet in front of the name of a file indicates that this file is part of the theme. The black bullet means it is a part of the "default" theme.
If you modify a file belonging to the "default" theme, it will be copied into the theme you are currently using.
To edit a file, click on its name to display its content in the edition area. If the file can be written, you will be able to save your modifications by ckicking on "save".
The modifications are applied immediately after saving, so be careful.
To help modify your templates, you may consult the template tag list.