Authoritative server?

Hey everyone, my name is Tz and I am developing a Multiplayer first person shooter and read up that Authoritative servers are better, because of cheating etc. I have looked around and cannot find any tutorials on how to do it, so can someone please leave the basics for sending client input to the server and then back the client to move it, or how ever it works? Thanks TZ P.S sorry for the generic question.