See the left menu for the different topics.
Where to find what?
1 Plugin options
In the WordPress backend, go to Plugins → DirectEdit (url: /wp-admin/plugins.php?page=direct-edit).
2 Template functions
Template files are stored on the server in this folder: /wp-admin/themes/[theme name]/ Use ftp to access these files.
3 plugin files
If you want to tweak DirectEdit in detail, first use the "copy files to current theme" button on the plugin options page.
All files will be copied to /wp-admin/themes/[theme name]/direct-edit/ where you can edit them for your purpose.