You just go to new game...I think. That's atleast what you do in Pokemon pearl or diamond
Chat with our AI personalities
relese all of your Pokemon and restart the game don't listen to that idiot,at the point in the game if you are the champion and everything then your at the after-game and you can whatever you want with it,you can continue playing and catching Pokemon,or you can restart the game or whatever else there is to do
go to new game and do what it says then you will erase your game
You start a new game and start over.
hit new game in the menu
to restart you press start a new game