ClassicPress contains two built-in editors that allow you to edit plugin and theme files directly from your browser. They are called the Plugin File Editor and Theme File Editor.
For security reasons the File Editor is disabled in new installations.
If you want to enable the File Editor, you should edit your wp-config.php file.
In your site’s dashboard then go to Plugins > Plugin File Editor or Appearance > Editor, select the specific plugin or theme from the dropdown on the right, and edit the file(s).
Please note that files must be writable, otherwise you cannot edit them. This depends on the file permission set by your host.
Use the File Editor carefully. Editing your plugin or theme directly could break your site and your changes may be lost in future updates.
Because your changes may be lost in future updates, we do not recommend using the File Editor on any plugin and theme that is listed in the ClassicPress or WordPress (or any other) directory.