I suspect you'd go to your main/top tab and choose "Format -> Option Inspector" then search for "language" or "translation" and see what options your front end supports. Hebrew doesn't appear to be in mine.

If no one on the forum answers, it sounds to me like it's worth a call to Wolfram support. They'd know what is best to do.

But I have to ask: if you are running win10, does win10 support Hebrew out of the box? and can you use that to enter text with? If win10 doesn't support Hebrew can you expect mm to do so? (that's just a question - it may not matter. Support will know).

(I say ask support, because if there is not option I can find - there may be a reason why.)