The short answer is you can't. Workbench 9.5 is available only in English and is not currently localized.
Ups, are there any plans to localize the Workbench in future?
Is this mentioned somewhere in the documentation? (I have not found anything)
I can't say for certain but there are thoughts about localizing to Japanese for ES3 but nothing has been firmed up yet.
If you mean "this" being that Workbench is available only in English, I don't believe we specifically point this but we'll take a look into it and get back to you.