Instructions
Mount the target on a surface with suitable stopping power, such as layered pads. Hay or styrofoam will not stop the bolt, particularly at close range. Stand about 10 yards from your target.
Cock the crossbow and aim at the center of the target. Hold your aim and slowly squeeze the trigger until the bolt fires. Maintain your aim throughout the process. Do this three times and check your bolt group. If the bolts are relatively close, approximately within a inch of each other, then you're ready to start sighting in your crossbow. If not, continue to practice until your shooting improves.
Estimate the correction necessary to align your scope with your bolt group. For instance, if your group is low and to the left, adjust your sight up and to the right. Continue shooting groups of three and correcting the sight as needed. The sighting process for a crossbow is largely trial and error.
Move out to range of 20 yards, once you have your crossbow sighted in for 10 yards. Shoot a group of three bolts at your target and make any necessary corrections until you are satisfied.