Instructions
Insert your Game Boy Advance "Pokemon" game into the Nintendo DS cartridge slot at the bottom of the system.
Turn the DS on and select the "Pokemon Diamond" icon. Press "Start" to begin the game and select your save file.
Transfer to Route 228 and enter Pal Park. Speak with the attendant to begin the connection process.
Select the six Pokemon you wish to transfer and complete the capture mini-game. The capture mini-game consists of you roaming around a small area until you encounter and catch all six Pokemon. It's fairly straightforward and should not take long to complete. Once the game has been completed, all six Pokemon from your Game Boy Advance game will be transferred onto your copy of "Pokemon Diamond."