To use the Relocator, you need two DS systems, the model of which is irrelevant. The DS with Pokémon Black & White will send out a DS Download Play program over wireless. Access this over the DS Download Play option in the DS's main menu for the DS holding Diamond, Pearl, Platinum, HeartGold & SoulSilver. This will load up the system.
This system does not transfer just any Pokémon but will allow you to select certain event Pokémon and send them over to Pokémon Black & White. For transferring of your own Pokémon, you will need to utilise the PokéTransfer after the main game is complete.
The Pokémon you can transfer aren't just any Pokémon of a specific species but rather specific event Pokémon that have been given away. The Pokémon that you have the ability to transfer are as follows;