Scott N pretty much nailed the bore sighting, but let's take it a step further and sight in with a similar trick.
You've got the rifle bore sighted so now fire one round at the target that we assume will hit the paper somewhere outside of the bull. Assuming there is little or no wind, and your shot felt good, you should be able to assume that the rifle will be able to print subsequent shots within 1" on either side of that bullet hole, resulting in roughly a 2" group. If you cannot see the bullet hole through your scope go to the target and mark the bullet hole with something that will be visible, a sticky or a piece of tape of contrasting color is fine.
Go back to the firing line and again sight through the scope so the reticle covers the bullseye. Now, without moving the rifle, adjust the scope until the reticle covers the bullet hole. Most scopes adjust in quarter minute increments in which case 4 clicks of counter clockwise elevation adjustment will raise the point of impact (POI) 1" @100 yards. Likewise, 4 clicks counter clockwise of windage adjustment will move the POI 1" to the right. This value equates to .5" @50 yards, 1" @ 100 yards, 2" @ 200 yards, 3" @300 yards etc. It will be useful to see if the scope adjustment is giving you a true value shift in the POI, and this information should be recorded. Get in the habit of good record keeping.
Your next shot should confirm a 100 yard zero. If the center of a 3 or 5 shot group does not center on your point of aim (POA), a further adjustment might be necessary. Once you are satisfied with the zero of the rifle, you can move the dial indicator so the adjustment of each turret is set to 0. This indicator is most often just held by friction on hunting scopes and is held in place with an allen screw, or several allen screws on scopes with target or tactical turrets. Zeroing the dials might be useful in the future if you wish to precisely dial in for a longer range or compensate for wind, or even for adjusting from one load to another.
