arceus isn't playable in the game but there is a dungeon where you see a statue of it
No but you see a statue of arceus and you get the Space Globe.
http://bulbapedia.bulbagarden.net/wiki/Arceus is a good place to see it.
R-see-us
you must get the azure flute and go to spear pillar.Use it and you will see arceus on a staircase.
You need to get the azure flute (event) and go to spear pillar. steps will appear and take you to arceus
You can't Arceus is no playable character. If you go to smashbros.com you can see all available characters.
If you have arceus, you go to the ruins of alph and you talk to a man and he will be suprised that you have arceus and then you will see Cynthia and she will tell you to choose Palkia, Dialga, or Giratina
Arceus: Get the Azure Flute from the Green Messenger Man at the Pokemon Mart. Then go to the Spear Pillar on Mount Coronet. As soon as you get there, the flute will play and a staircase will appear leading to the Hall of Origin. Then, you will see Arceus at the end at level 80.
You will need an azure flute though. Go to Mt. Cornet top where you see dialga and use the azure flute right at the entrence and stairs will appear. Go up them and walk forward and you will see arceus.
Arceus: Get the Azure Flute from the Green Messenger Man at the Pokemon Mart. Then go to the Spear Pillar on Mount Coronet. As soon as you get there, the flute will play and a staircase will appear leading to the Hall of Origin. Then, you will see Arceus at the end at level 80.
There is not an arceus trophy, and arceus was created after brawl, so arceus is not in brawl