How To Get Arceus In HeartGold?

If you went to Toys R Us awhile back, you would have received a special Arceus.

If you take this Arceus to the ruins in heart gold, it will take you to the Sinjoh Ruins (A place in between sinnoh and johto). Once you are there Cynthia will tell you about arceus, and then arceus will reward you with a egg (that hatches once you get it) of dialga, palkia, and giratina.