It works like a mastery that can do almost anything. If you need to heal someone, you just put in your energy in the power cosmic to heal and you heal someone according to the healing, magical action. If you want to use it as a force blast...
It also says that you can change your Abilities/Action numbers at will, which for game balance I interpret as 'May add to (Physical)Abilities/(Any)Actions' AN up to Power Cosmic AN; May change the bonus every panel through use of this action'
So if someone has Power Cosmic 10, he could have, say, +3 to Str, +2 to Durability, +2 to Agility and +3 to Speed, no need to spend stones to maintain. If, say 3 hours later, he needs more Strength, he could spend like 5 stones to gain +5 Strength instead of what he had before, or 10 to gain +5 Str and any other boosts, etc.
That's just how I do it though; the description is pretty vague so it probably depends on the GM.
Otherwise Ricochet has it right; it's basically Alter Reality with a limit, lol.
Nothing is impossible, it just hasn't been done yet.