Have you done all these steps?
I have already Check the box next to Enable Knowledge base (Client interface), but it still doesn't show.
You need at least one public category.
You need at least one FAQ in a public category.
That FAQ must be set to type public. In fact the radio button for this has the deceptive text "Public (publish)." It does make the FAQ public but it does not publish it (make it visible, rather than it being an invisible draft of what may become a public document). I wasted a few hours on that.
Final step, after saving changes, is to select "Publish FAQ" and click "go."
Miss any of those steps and there are no client-facing FAQs.