Shoot a couple of groups with field points and include one or two broadhead tipped arrows. Shoot from a 20-30 yd distance and determine a consistent impact point of the field points verses broadheads.
Move the rest in very small increments away from the broadhead. eg..if the broadhead is impacting to the right of the field points then move the rest to the left. After every adjustment shoot a group and check the impact points.
You may or may not have to adjust your sights. often the adjustments are so minute that the sight in will not be affected. this method will superfine your center shot and you’ll be ready to shoot a fixed blade broadhead.
this method also works for elevation. simply move the rest up or down in 1/64th adjustments