OK, here's a quick snapshot. There are 3 screws. You just rotate the focus ring to align with each one. Make sure you get a good-fitting screwdriver so that you don't round them off. Adjust minimally, perhaps 1/8 to 1/4 of a turn.
EDIT: Note - apparently, there have been some stories of success with this adjustment, and some stories that claim no improvement was made. Since my lens didn't have creep issues to begin with, I can't state with certainty that adjusting these screws did improve things. I note that later in the thread, somebody did adjust them a great deal and claimed no improvement. So, I guess it's fair to say "tweak at your own risk", since the reward is questionable.