How do you battle over the Nintendo WFC in Pokemon DP?

Answer 1

To battle on the Nintendo WFC in Pokemon DP:

1. First of all you must register your friends' Friend Codes in your Pal Pad which is obtained by going to the basement of any Pokemon Center. Please note that your friends must also have your Friend Code registered in their Pal Pad.
2. Go to the basement of any Pokemon Center.
3. Talk to a receptionist at the second counter.
4. She will ask you if you wish to connect to Nintendo WFC. Answer "Yes".
5. A screen will appear which shows your Friends' connection status. If they are connected, select the person whom you'd like to interact with and press the A button.
6. In the menu that appears, select "Invite" and then either "Single Battle" or "Double Battle", depending on the type of Battle you and your Friend wish to have.
7. If your Friend is inviting you for a Battle or Trade, you will see an orange icon. There is a different icon for Battle and a different one for Trade. If you wish to accept the invitation, select the Friend and select "Apply" in the menu.