I’ve found truths incredibly flexible to give a very quick set of bullet points for a scene, however conversely, I feel they are mostly there for you, the GM. You jot them down to a scene to establish the baseline (Example Scene truths - Raining, Strong Winds, thunder and lightning) and simply describe the scene as such. A truth is often nothing more than a normal thing the players interact with. For my players, I described it roughly as follows.
“A truth is a factual element of the world, something that exists without question. An example would be a wall is well maintained and sturdy. Players and the GM can interact with truths, to alter the fundamental state of the truth in question. For example, a character can take a sledgehammer to a the wall and change that walls truth from ‘sturdy’ to broken. And so on. Q truth can also describe a key characteristic of a person or thing, that John is a ‘Keen Marksman’ or Fred is a ‘Yellow-bellied Coward’, in this case a truth is simply something that is factual about a person’s character. Simply put, a truth is a simple shorthand for demonstrating the factual state of a thing, a quick way of confirming the facts about a person, thing or idea.”
That may be a bit flowery, but hopefully that helps! Main thing is to remind people that truths can change as time goes on.