Instructions
Walk with your Pokéwalker until you have unlocked paths 1 through 9. Each path takes a certain number of watts to unlock, and watts can only be gained by walking.
Defeat the Champion of the Pokémon League in "Pokémon HeartGold" or "SoulSilver." Next, defeat Professor Elm's Kimono Girls. Once finished, speak with Professor Oak to obtain the National Pokédex. This item allows you to unlock paths 10 through 20 on your Pokéwalker.
Continue walking with the device to unlock the remaining 11 paths.
Wait until Nintendo holds an official Pokémon event that opens the path. You can attend these events using your Nintendo DS's Wi-Fi connection or by visiting a Pokémon tournament or special promotion.
Download the Winner's Path directly from Nintendo and walk it to discover new Pokémon.