Shoot at the spot you are using to set your sight: then leave that pin setting as is. Put a red spot on the hole the arrow made if it is not on the spot you shot at.

Now set the pin you plan to use for that distance in the other sight groove.
Set this pin on the red spot that marks the arrow hole: while the first pin used to shoot is setting on the original spot you shot at.

Now the first pin in the first groove is aiming at the original spot you shot at; and the second pin in the second groove is aiming at the red spot where the arrow point hit. So this second pin is set on target.

Above I said shoot an arrow to mark a spot for simplicity, but you may wish to shoot 3 or more to mark a spot & calculate a mean, for more precision.