Close the wall pocket door far enough to expose both carriages at the top of the door.
Turn the hex nut--shaped adjusting pin on the bottom of the carriages with an open-end wrench.
Turn the pin clockwise to raise the side of the door suspended from that carriage, or counterclockwise to lower the door.
Adjust the entire door upward until it clears the floor and slides easily.
Adjust the sides of the door independently until the door hangs straight in the doorway and closes flush against the jamb. Slide the door open and closed several times to make sure it's operating properly. Make any further adjustments as necessary.