The simple answer can get complicated, but it is actually easy once you get the hang of it. I'll probably miss a lot of little nuances, but here goes...
Because you have a FFP scope, you have hash marks on the reticle, and possibly numbers as well. Those hash marks and numbers correspond with the turret dial numbers and hash marks. Look at the scope manufacturer's diagram of the reticle to know exactly which hash marks correspond with which number and hash marks on the turret dials.
Then, once you have a good idea of how they correspond, you can shoot at the bullseye a few times to establish a group on the target. It does not matter where this group hits on or off the target. You then look through the scope and use the hash marks on the reticle to measure the group's distance up and down and left and right from the bullseye. At this point you simply turn the dials the correct number of hash marks, as they appear in the scope, to move the reticle to the required location.
A not so easy way to do the same thing is, after shooting a group, align the scope back on the bullseye and then turn the dials until the cross hairs and on top of the group. I find that this is harder than measuring and counting clicks because the rifle always seems to move when dialing.
I would zero that Impact at 40 yards. This will give you a very flat shooting gun from 20 yards out to 50 yards. After that you can hold over using the hash marks or dial the scope.