Not sure what I did, but my faucet is a delta. With a single lever. I've replaced the inner parts before ( the springs) but this time the water won't flow. I disassembled it again and turned on the water and the water flows, but soon as I reassemble, the water doesn't flow... I'm not savvy in plumbing, so please respond with simple instructions

Take the aerator off the end of the spout and see if water comes out.

I don't know what that is

Make sure you lined up the slot on the ball before reassembly. Otherwise the holes don't line up. PS Aerator is the screen on the end of the faucet nozzle.

That little thing on the end of the spout. Usually you can unscrew it with your hand. Some times you have to use a pair of pliers. If you use pliers, wrap several wraps of tape around it so you don't scar it up with the pliers.
It breaks the stream of water up into lots of little streams so the water doesn't splash. It can get stopped up with debris.

Make sure you lined up the slot on the ball before reassembly. Otherwise the holes don't line up. PS Aerator is the screen on the end of the faucet nozzle.
Okay, I'll try. Thank you

Make sure you lined up the slot on the ball before reassembly. Otherwise the holes don't line up. PS Aerator is the screen on the end of the faucet nozzle.
I made sure to line ball up with the slot and removed aerator, still no water. :-(

If water flows without the ball and does not with the ball installed you either have assembled it wrong or the holes in the ball are clogged. The Delta design is pretty basic and works well. Also check the main spout to be sure it's open.

I made sure to line ball up with the slot and removed aerator, still no water. :-(
So... water is sitting out the wrong hole and I can't turn the water off anymore

so... water is sitting out the wrong hole and I can't turn the water off anymore

Lets try again. 2 springs go in the inside water hole and the seal sits down over them. Make sure the seals push down into the hole. Line up the little pin on the side so it fits into the slot on the ball. Put the plastic spacers and nut over the ball point. Tighten nut. Align the handle so it slips onto the pin and fits on rotating faucet part. Screw it down or tighten the Allen screw depending on model. Turn water back on.