Let $G$ be a finite group and $Rep(G)$ denote the set of all the irreducuble representations of $G$ (up to isomorphism, of course, so it is a finite set).
The problem is to define an action of $Aut(G)$ on $Rep(G)$ (the field is not mentioned so I guess it doesn't depend on the filed) and prove that inner automorphisms act trivially.
It must be something very standard by I don't know how am I supposed to come up with it. I am sure I would be able to do the second part if I knew what the action is.