Do you have any previous dev experiance?
That changes the answer. :)
There were a good number of changes in WoW since WotLK. You need to fire it up in Cata and see what breaks.
Probalby the biggest thing is that the "this" global variable no longer works which had been deprecated for some time already.
You need someting to edit the files with, and you need to use soemthing like wowwiki as a reference for how AddOns work.
This version of AddOn Studio is enough out fo date that I woudlnt suggest using it if you are just starting. There is an updated one here:
See the other discussion for hwo to create an addon in this forum to give you a small taste of what you are in for, and it contextually should give you a realy good idea of how it all basically works.