BC is probably on the Ammo box, or look it up on the manufacturer's website.
Muzzle velocity you measure with a chronometer. Or look it on the Ammo box, or look it up on the manufacturer's website, that will be for a generic barrel length.
Sight height, distance from muzzle center to front sight tip or Scope front center.
Zero, whatever distance you zeroed at.
Pressure and temperature from a weather website for your area. This will vary.
So type in the above values, type in the range to the target, and you will see the drop in inches and the number of clicks (1/4 Moa) to adjust the vertical elevation turret for the drop. Most people aim off for windage, or you can use the number of clicks on the windage section.
If the drop is 6" and 15 clicks, you aim 6" high, or turn the elevation turret in the direction of the scope's "up" arrow 15 clicks. It is good to mark the elevation and windage turret positions when you zero the rifle. If the calculator says go up 30 clicks for a different range, that is 30 clicks from your zero setting.