I will give you an A + for the graphics!
What caliber is the rifle?
Is this rifle going to be used as a target gun or is He going to hunt with it?
what distance do you want to set your zero at? ( 100 yrds, 200 yrds )
this should be set at the distance He would be comfortable shooting at.
The bore site should help you out a lot, They are intended to get you close at 75-100 yrds. and you adjust your wind-age and elevation so you can find paper. and then its fine tuning.
Get a ballistics chart for you caliber so you can determine the bullets flight path as it travels from the barrel out to 300-400 yrds. this will allow you to visualize the arc at which the bullet travels in flight and you can predict hold over or under for the distances closer to, or further out, past your selected zero.