I want emphasize the importance of getting the tension on this screw just right. If it's too loose the stock will be loose and become battered and probably split. Too tight, and the relationship of the triggers to the sears and the safety's proper function is messed up. If it's really overtightened, it can cause the trigger blades to bear on the sears so tightly that the sear noses are partially pulled out of the hammer notches and the gun can discharge without warning.
The screw slot should have been indexed properly when it was assembled so that is your indicator of proper position. These screws are put in quite tightly originally so be sure you are not a full turn too loose. If it goes past proper aligment more than just a little bit, and won't stay tight, it should be rebedded as another poster mentioned.
This is all a long way of saying if you really don't know how to do this job, take it to a good gunsmith.
