Trade Eevee

• 1). Turn on both DS systems, one with the "Pokemon SoulSilver" game cartridge loaded and the other with the "Diamond," "Pearl" or "Platinum" game cartridge loaded.
  
  
• 2). Visit a Pokemon Center in both games and walk to the second floor to access the Wireless Union Room. An icon representing the player from each game appears in the room.
  
  
• 3). Walk up to the other player, press the "A" button and choose the command "Trade."
  
  
• 4). Highlight Evee to trade in the "SoulSilver" game and highlight any other Pokemon in the other game.
  
  
• 5). Select the "Exit" command when the trade concludes and send each player to the door to exit the Union Room. Put the DS with the "SoulSilver" game aside for now.
  
  

Evolve Eevee in Eterna Forest

• 1). Walk or fly from your current location in the "Diamond," "Pearl," or "Platinum" game to Eterna City, located on the western side of the game map.
  
  
• 2). Walk west from the city to Route 205 and enter Eterna Forest.
  
  
• 3). Walk south in the forest until you pass the rocky walls, then turn west. The moss-covered rock sits in the upper left corner on the western side of the forest.
  
  
• 4). Stand next to the rock. Press the "X" button to access your inventory and select the "Rare Candy" in your "Items" pocket.
  
  
• 5). Choose the command "Use" and highlight Eevee as the Pokemon on which to use the item. Eevee evolves into Leafeon as soon as it eats the candy.
  
  
• 6). Return to any Pokemon Center in the game and use the Wireless Union Room to trade Leafeon back to your "SoulSilver" game.