Language cannot be changed in JDM models.
If you want a owners manual for prius, try google. "Prius Owners manual" click the very first result (from toyota) and then select your car model and download or view these manuals online. These manuals are in English language from Prius USA models. So far, I have found that instructions show are workable on the Japanese MFD as well, but the language option is not available.