Things You'll Need
Instructions
Using Action Replay
Insert the Action Replay device into the Nintendo DS, and then insert "Pokemon Pearl" into the slot on top of the device. Turn on the Nintendo DS.
Enter the following code: "94000130 FCFF0000 B21C4D28 00000000 B0000004 00000000 10001170 00000181 D2000000 00000000."
Save the code and select it from the "Codes" menu.
Press the "Start" button to begin the game.
Go to the Mining Museum in Oreburgh City and hold down the "L" and "R" buttons while entering the building. Talk to the professor to get Jirachi.
In Pal Park
Go to Pal Park.
Head to the mountain region of the park.
Run around in that area until you encounter a Jirachi. This may take a long time, as many other types of Pokemon live in the mountain area, and Jirachi is a very rare Pokemon. Keep fighting off Pokemon until you find a Jirachi.
Weaken Jirachi in battle and use a high-level pokeball -- such as an Ultraball -- to capture the Pokemon when its health is low. Jirachi is a steel/psychic-type Pokemon, and it is weakest against ground- and fire-type Pokemon, which get double hit points against Jirachi.