Instructions
Visit Pokemon.com and click on "News and Events." On the next page, click on "Video Game News."
Browse through the current listings of Nintendo events to see whether an event for "Pokemon Pearl/Diamond" is coming up. Click on "Read more" if an event is being held for the Azure Flute. You will be informed about event details such as time and location.
Turn on your game and select "Mystery Gift" from the main menu if the event is available online. Select "Receive Gift" and "Get Via Wireless." The Azure Flute will appear in your inventory.
Travel to the physical location of an event at the scheduled time if it is not online. Common locations for Nintendo events include GameStop and Toys R Us. At the event, the Azure Flute is obtained the same way as described in Step 3, by using the "Mystery Gift" option.