for me the aiming had to do with being able to offset from the pivot point. If theres no offset its pretty simple vector math (source vector - target vector)
for offsets you need something along these lines UE4 - Offset Turret Rotation Tutorial - YouTube
this isnt the video i found way back, but its the same principle.
Find the radius, find the intersection, find the delta, apply
I tend to lean on the sphere intersection equation to determine these details.
Thats the basis, but implmentation is based on your needs and complexity