1/ Zero at about 30 yards, your book will say 100 yards as 1 click will be 1/4" at that distance
2/ For 3 - 9 zoom use the 6x zoom to zero and it should be bang on at 3x or 9x zoom
3/ Mil-dots are for different ranges, 1 up for 40 yards if zeroed at 30 yards, 1 down for 20 yards. The left and right mil-dots are for cross winds, 1 is about 7 mph cross winds. Place Targets from 10 yards out every 5 yards apart to get used to the Mil-dots