Turn on the sprinkler system. It's easier to accurately adjust the spray level while the sprinkler runs. A raincoat or other type of water-resistant clothing may be desirable for this job.
Stand next to the sprinkler head and locate the spray adjustment screw on the top. Turn the screw clockwise to reduce the pressure and create or a shorter spray, or turn it counter-clockwise to increase pressure and create a wider spray.
Stand back and observe the adjustments. Confirm that the water reaches all of the nearby plants.
Make any small adjustments, if necessary.