Nobody's managed it yet, so far people have only renamed moves and edited their effects with a program such as A-tack
This hasn't been achieved either. I think there were some people looking into it, but nothing's really come of it so far- for now, you can use the 25 "empty" slots, or replace other Pokemon.
ASM. Which is like extreme scripting, so it'd be too difficult for a beginner to manage.
I don't know if you can- as with attacks and Pokemon, you can edit existing ones to suit your needs with a tool such as ItemEd or something.
Try another patch thing, or learn ASM- simple as that.
Google is your friend, on that one.
In future, please don't make a new thread for questions, as it won't be approved. Instead, use the Simple Questions Thread, in the Beginner's Lounge.