Hello,
one you have your zero like you said, engage the thumb locking screw. now unscrew that huge flat head cap that is on top of the scope turret. now spin 1-8 dial till you hit 1 some times due to compresion and dirt and gunk over the years they stick so might have to pry it a tiny bit with a toothpick VERY gingerly, most just pop off with you hand. good luck
later
vaughn