Hmm, I have Bits and Pieces of Plot but...

[Allucard]

Ok, I need to organize myself.

I have a Phsychokinetisist who is just now manifesting his powers, The world is post-apokalyptic, civilization is returning to normal but its in a more medieval stage. Ammo is running low so most people use medieval made weaponry. Mutants and evil things run rampant...

I need somthing the two characters have to do, why they are doing it, and a bad guy... those are my holes...

[DyingWhiteLotus]

Hi there. I think that this could be pretty interesting...

I was thinking, maybe there is some sort of source from which the evil is stemming...And they want to close it somehow? (Maybe not that original :P )

[Kestrel]

First thing you need to know is this: We are intelligent species now. The dark ages were a low in human culture, warfare and ethics. To go back to medieval settings requires you to make people complete idiots. Censorship seems to be the easiest way, but it is going to take you hell more than just that simple paragraph of thought to figure out how that became successful. Y'see, that is a huge issue when working from the modern world: evolution of the environment.

The Romans did way better than knights anyway. So unless you have some very good excuses, no sane person is going with a poorly organised offence. If all of us ran out of ammunition, we would still try to find a way to stick to ranged combat. Explosives are easy to create, so we'd have options for heavy assaults (hello catapult) and if you can create explosives, it is probably also very possible to create some kinda gas-grenades. Haven't delved too deep into this, which is your task anyway, but going back to swords and shields is plain stupidity with the knowledge we have today.

And naturally, you're going to need answers on history and physics. What happened before the apocalypse came? What caused it? How did humankind rebuild? Did they rebuild at all? How have mentalities and politics changed? How do they function nowadays? How does daily life look like?

Why are there mutants? Why did people/mutants become downright evil? What is your view on the term 'evil'? etc.

If you can answer all of those questions, you've started to create a world. Naturally any world has issues. out of which you can pull a plot. Then think of who would be involved in such a plot, and boom, you answered your own questions!