Presumably the same way that a laser sight for a gun works? I assume you adjust it to compensate for the arc of the projectile at a given range?
Exactly so. No different to any other sight.
Even if a bullet or arrow travelled in a straight line you'd still need to compensate for distance, even with a laser sight (depending on how far from the muzzle/arrow you mounted the laser).
That's the counter-intuitive part of rifle shooting, especially with a big "Scope". Bullets initially fly low, then they cross your line-of-sight, then they fly high, then they cross line-of-sight again. When you adjust a sigh for elevation you are moving, forwards/backwards, the point(s) when the projectile crosses the line-of-sight by raising/lowering the gun barrel. The sight never changes, that stays pointing at the target, it's the weapon underneath that moves.
Nobody ever shot anyone far away by aiming directly at them.
I suppose you could get clever with a Laser gun, Laser sight and some mirrors to create a "point-directly-at-it" weapon.
When all else fails, especially in Archery at 100 yards, you just aim at a distant tree, above what you want to hit. If you hit the target then keep aiming at the same bit of tree. If not, aim at a different bit of tree. If you actually hit the distant tree then you are probably shooting a Compound bow.
