How to use …

Hi everybody,
I’m trying to install QTranslate Extension. I read everywhere this:
Simply add the class “multilanguage-input” to all the elements which you want to get multilanguage (input-text, textarea). It will make the elements multilanguage, so the information will be saved using the qtranslate structure <!–:en–>Content EN<!–:–><!–:es–>Contenido ES<!–:–>
But can somebody tell me where I have to add this code please?

Thanks very much

http://wordpress.org/plugins/qtranslate-extended/