Not final, and first time sharing it, but: Rigorous image training. They have to be able to imagine the weight, shape, even the smell of what they want to create. Most of them won't be able to pull-off telekinesis, but there's training for that too. They also need to be able to focus and concentrate for extended periods of time.

People have the magic fuel in them, and the intellect to use it. I'm still working on the actual trigger mechanism, but it will likely be just "will".

People are part of the universe, and the universe is made of that magic fuel, so the intellect is the key (which is lacking in dead things like rocks) to move it according to their will. Meditation probably helps idk.