The long range target has the target turrets that are under removable caps. Not like the M1 or M3 turrets that do not have removable caps and are sealed and always in the open.
Once you zero your rifle, use the allen wrench that came with your scope, loosen the three small allen set screws on the top outside edge of your turret, the outside sleeve with the numbers and slash marks should turn easily as long as you loosened them far enough. The sleeve is all that turns, the silver part in the middle of the turret should not and if it does, loosen the set screws more. Move the outer sleeve so that the 0 lines up with the slash mark on the base of the turret housing. Gently tighten the set screws so you do not strip them. Now do the same for the windage turret.