How do I use an aim offset in a third person template

In my game the character will be able to shoot fireballs but I want him to be able to aim down the point how can I do that?

Have you tried to follow it? Literally! step by step!
This is for the Third Person Template

Creating an Aim Offset:

PS.:It may sound complicated, but it is not complicated.

From what I can understand you want to align the aim offset to the point under the screen center/under mouse cursor?

In ainoffset mode, attaching a crosshair to weapon?