I just replaced the seat and springs and the stems on my bathroom sink. When I turned the supply line on, the water runs like the handle is turned on. I have tried everything I know to try. Please help.

Remove stems, turn 180 degrees and reinstall.

It looks like you have Delta faucet. You probably didn't seat the ball the right way ( there is a little slit on the ball and peg inside the faucet and they need to go together. ) Or, there is a plastic piece on top of the faucet where handle stem penetrates ( it has shape of a tear ) .. and this piece is not lined up with the narrow part towards the front ( 6 o'clock) . Check these two things out and let me know if that helped. Back to you. Milo