^^^
To elaborate a bit, once your scope is mounted place the rifle in a rest if possible, or as stable as you can get it with a front bag at minimum. If you're at the range (you can also do this at home sighting in at any object at least 50 yards or so away preferably), remove the bolt and while looking down the bore from behind the rifle, position it so that the center of your target is in the center of the bore.
Without moving the rifle (and this is the critical part- and why a rest that will lock it in place is preferred), sight through your scope, and move the crosshairs to the bullseye or center of your target. Then sight back down the bore and confirm you didn't move the rifle while doing this.
Once you have confirmed the center of your bore is center of target, and the crosshairs are centered on it as well, you should be on paper.
If not, just place any object on the berm behind the target, and have a spotter walk you into it. This is what I usually end up doing with autoloaders where I can't sight down the bore.