Where is the door to Tabuu in Super Smash Bros Brawl?

You go to where you get Donkey Kong,then you go to the purple arrow you go into the door.Then there is going to be a big door in the back ground.Of course go into it.There will be a cutsing then you will meet Sonic there.Then you will get to choose 6 characters.Then you fight Tabuu!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!