Go to the Pokemon center and in the PC select a Pokemon and click release
Chat with our AI personalities
Click new game at the menu
Either trade from a differnt game or cheats. Only way(s).
Technically,yes you can get Arceus in Pokemon Heartgold,but only by trading it to your Pokemon Heartgold game from Pokemon diamond,pearl or platinum.
First you delete your save game, edit the contents of the game chip... Just kidding! REAL ANSWER: you can't, sorry dude.
Pokemon HeartGold, SouldSilver