Wash your hands in antibacterial soap and hot water and dry them with a clean paper towel.
Grip your lower lip with the thumb and forefinger of your non-dominant hand. Use your index finger to press the back of the labret stud toward your lip so that the bead sticks out a few centimeters.
Use the thumb and forefinger of your dominant hand to unscrew the bead in a counter-clockwise direction.
Pull the bar out through the back of your lip.
Insert the new labret stud, with the flat back attached, through the back of your lip. Press it forward so the bar sticks out a few centimeters, just as you did before.
Screw the new bead on in a clockwise direction.