how to enable user submissions from front end?

I was trying to preview a post from the backend, only to discover on this forum that that is not possible. An amazing limitation but that's another question. Seems I have to go to the front end to be able to preview a post before I publish it, but I don't see any button/link that allows that so I'm guessing it's somewhere in the configuration.

But no easy link to documentation and the forum has no answer to the question above. Can you help?