Big piece of cardboard - 4x4 slip sheets are nice. 25 - 40 yards depending on your preference.
Draw a black dot (baseball size) with a sharpie.
From a bench with both a front and rear bag, shoot at the dot.
Walk to the cardboard and find the center of your pattern.
Draw another black dot with the sharpie in the center of your pattern.
Return to the bench and place the gun back on the bags.
Place the red dot on the first black sharpie dot.
Without letting the gun move, use the supplied screw driver to move the red dot to the black dot in the center of the pattern.
Shoot to confirm. It'll require some tweaking with different loads etc.
Make sure to loosen the set screws before turning the adjustment screws. I always try to center the red dot in the Fastfire over the barrel before I shoot. Pretty simple really.
The mount came today, I plan on hunting Friday morning and don't think I'll have time to shoot it in tomorrow.
Thanks