You can get your Friend Code from the Pal Pad in your Key Items pocket. If you don't have it, once you get the Coal Badge, you can get it from the basement of any Poké Center.
You can battle either from the Wi-Fi Club, which is in the basement, or from the Battle Frontier. The Wi-Fi Club is easier if you know who you want to battle against, or even if you have a RL friend to do silly battles with.
You only need a wireless router to use Wi-Fi, and if you don't have one, then you need a special connector dealy to use with your DS. The Nintendo website details how to set up your DS with their Wi-Fi connection.
You can battle either from the Wi-Fi Club, which is in the basement, or from the Battle Frontier. The Wi-Fi Club is easier if you know who you want to battle against, or even if you have a RL friend to do silly battles with.
You only need a wireless router to use Wi-Fi, and if you don't have one, then you need a special connector dealy to use with your DS. The Nintendo website details how to set up your DS with their Wi-Fi connection.