language switcher

I have an english blog up and running and I would like to make a button to change the language of the entire blog to french. I’m reading up on plugins that can do this (right now gengo) but I’m alittle but confused. Is this plug in meant to do what I want? Or simply change the language of the admin dashboard.

I have all the text already translated, so I’m not looking for a plug in to translate the text for me, just swtich in the french text for the english text when the french/english button is clicked.

many thanks