If this is a typical Cooey 60 rear sight, the sight base has "wings" on the front where it screws into the dovetail keeper. You can adjust the rear sight but will have to remove the rear sight from the base and push the base the same direction you want the impact to go, then put the sight back on, shoot to test (repeat if necessary). It might be easier to adjust the front sight if it is dovetailed.
If you want to adjust your impact to the left, push your front sight to the right. Vice versa for adjusting the impact to the right.