How to display Hebrew text

I am listening to a Rabbi talking about Torah. On his website, he has available PPT presentations that follow the discussion. They are (presumably) in Hebrew. When I download them, there's just a bunch of "NLT KCUO JJHFUO."

I have activated a Hebrew keyboard, and added a Hebrew Font (New Peninem MT) though if I convert the text in the Keynote slide to the new font, it doesn't automatically convert. I have to duplicate the slide, delete the text, then transcribe the original -- typing a bunch of nonsense BACKWARDS -- in order to make the presentation look like what it's supposed to be.

There MUST be a proper way to do this, but I haven't figured it out. What shall I do?

thank you