This is from the Nightforce manual, but should help you out.
Step Five
Focusing the eyepiece - this procedure focuses the reticle to your eye. (This has no effect on the image unless severely out of adjustment).
(1) Check that the riflescope is set at the highest magnification.
(2) Set the parallax adjustment to the infinity setting [ ∞ ] on the riflescope.
(3) Look through the riflescope eyepiece to determine if the reticle is clear and in focus instantly. Note: All Nightforce
riflescopes are factory set for an average individual eye strength, thus adjustment may not be necessary. Looking at the
reticle for an extended period of time during this process will cause your eye to compensate, resulting in false indication of
reticle focus.
(4) If adjustment is necessary grasp the eyepiece and rotate counter clockwise – loosening it away from the lock-ring while
holding the riflescope from turning in the rings. Several turns of the eyepiece are necessary to achieve any measurable
affect. Once reticle focus is achieved, lock the eyepiece by threading the lock-ring back to the eyepiece.
(5) Fast focus eyepiece. Not all Nightforce riflescopes are equipped with a lock-ring on the eyepiece. If your riflescope model is
equipped with a fast focus eyepiece ie. No locking ring, simply perform steps 1, 2 & 3 above to set eyepiece focus.
Final Step
First, level the rifle, then hang a plumb by a line at 100 yards. Rotate the riflescope in the rings until the vertical portion of the
reticle is parallel with the plumb line. Tighten rings evenly both front and rear until riflescope is secure.
