Things You'll Need
Instructions
Insert "Pokemon Platinum" into your Action Replay. Stick the Action Replay into your Nintendo DS unit until it clicks into the top slot. Start your DS and go to the main menu of the Action Replay. Use your DS stylus to select the green "Asterisk" button on the bottom screen.
Pick the "Add New Code" option on the screen. Look for "Pokemon Platinum" in the list of games. Give the cheat a name similar to "Azure Flute." Use the D-pad to enter the following code:
94000130 FCFF0000
62101D40 00000000
B2101D40 00000000
0000B5D4 0000000A
0000B5D8 00000000
D2000000 00000000
Select "Start" in the main menu of the Action Replay to begin "Pokemon Platinum." Talk to the Delivery Man in any PokeMart to get the Azure Flute. Make sure a Level 80 Fighting- or Rock-type Pokemon is in your party.
Travel to the Spear Pillar, which is located on the peak of Mt. Coronet. At the peak, the game will ask you whether you wish to blow into the Azure Flute. Select "Yes" to blow into the Azure Flute. A staircase will appear before you after you blow into the flute.
Walk up the long staircase. At the end, you will see Arceus. Save your game and press "A" before the Arceus to battle it. Use your Rock- or Fighting-type Pokemon to battle the Normal-type Legendary Pokemon. After you weaken the Arceus, throw Ultra Balls at it until you capture it.