Remove the doorknob using a screwdriver to loosen and pull away the screws mounting it to the door.
Remove the screws attached to the doorknob’s top and bottom and set them aside.
Apply a thin, even coat of spray lubricant inside the doorknob and over the mechanics. Twist the knob back and forth, spraying more lubricant as needed to turn it easily from side to side.
Reinsert the screws into the doorknob’s top and bottom.
Secure the doorknob to its original place using the screwdriver.