hey josue,
the text is handled in your easydiscuss language files. to change this you can use joomla's native language override function. that way your changes don't get overridden with every update so you don't have to do them over and over again. you can find more about language overrides here: http://stackideas.com/blog/how-to-override-joomla-language-strings

hope that helps and have a nice day