Pligg uses a centralized language file stored in the /languages directory, which contains all of the phrases used throughout Pligg. The language file will be named something similar to lang_english.conf, where "english" would change based on your website's language. You can either make edits to the file locally and overwrite the file stored on your server, or you can edit the language file from a web-based editor found in the Pligg Admin Panel. To access it from the Admin Panel, click on the Language tab across the top.
In order to edit the language file from the web-based editor, you will need to CHMOD 777 the language file.