Start at 25 yards, and use a rest, sandbags, or something to be really solid and still. Shoot 3 shots aimed at the bull. See where they hit, adjust the scope as the instructions say, and shoot 3 more, aimed at the bull again.
It is really important that you do not try to steer or guide the bullets. I have seen guys aim off to the side of the bull to try and make the bullets hit center. Do not do that, always aim at the center, and then adjust the scope to move the group into the center.
After you get the group where you want it, move the target to 50 yards, and repeat. When you are happy there, try 100, or 75 yards, or whatever you think is your max "point blank" range, where you want the POI (point of impact) to be the same as the POA (point of aim). I left mine at 50, and just hold over a little for longer shots, which I rarely shoot.