Spin the dials so the word "PACK" is spelled out in the viewing window, reading from the top of the lock to the bottom. Pull the shackle upward.
Turn the shackle 90 degrees counterclockwise so the notch on the shackle lines up with the groove in the body of the padlock. Push the shackle down.
Turn the shackle another 90 degrees counterclockwise so the open end is over the viewing window.
Spin the dials to your new word combination. Turn the shackle back clockwise 180 degrees and close it as normal.
Scramble the dials and your new code works immediately.