If the sprinkler you wish to adjust has a fixed pattern (meaning it sprays water in a fixed method and does not rotate or turn), you have what is called a spray head.
To review how to adjust the left to right pattern coverage of the spray head, first look at the designation on top of the nozzle. Many of the nozzles have certain patterns and arcs that are non-adjustable. For example a 12Q nozzle will throw a twelve- foot long quarter of a circle (90 degree) arc spray. The only thing that can be adjusted on these fixed arc nozzles is the distance the water is thrown. Turn it to the right (tighten the screw) to reduce the throw by up to 25%. You can also aim the nozzle by firmly grasping and turning the pop-up stem. The stem incorporates a ratchet that will hold the spray nozzle in its new orientation.
You may also have a Variable Arc Nozzle (VAN). If you have a VAN nozzle, it will say “VAN” on the top of the sprinkler with a number in from of the letters “VAN”. The number represents how far, in feet, the water will be thrown. To adjust the pattern on a VAN nozzle, pull up the stem of the sprinkler (as if it was on) and find the small black ring at the base of the nozzle at the top of the sprinkler stem. Turn this ring left or right to increase or decrease the pattern.