It's a pain, sort of. You turn it on. It warns you that it can't be used with the Zoom feature enabled. Once past that hurdle it gives you a notification about turning it on, and reads it. You try to tap OK, and it tells you OK. Only when you decide to double tap on OK, does it actually start working.
This becomes obvious later, when you touch an icon it reads the icon to you, and when you do nothing for a moment will tell you to double tap to activate the icon. Pretty much everything that was one tap, becomes a double tap. I suppose that makes sense. You don't want to be opening every app just to find out what app it was.