Instructions
Trading
Connect your DS to the Internet by first inserting the Pokemon Pearl game and accessing the game main menu. Select Nintendo Wi-Fi Connection Settings. Select "Connection 1" and then search for an Access Point. Select your wireless network. Once the DS has connected to your wireless network, Pokemon Pearl will be ready for wireless Pokemon trading.
Defeat Roark. The option of trading Pokemon in Pokemon Pearl is available after defeating Roark, the gym leader in Oreburgh City. When Roark is defeated, all Poke-centers become available trading spots.
Go downstairs in any Poke-center. Talk to the woman in the basement area and she will open the Pokemon trading window.
Trade any of your Pokemon with a contact for Umbreon. Once the trade is complete, you will have an Umbreon Pokemon, without having to do any of the work on your own.
Evolving Eevee
Collect Eevee. In order to evolve your Eevee and add Umbreon to your Pokedex, Eevee must be first collected. Because Eevee is a special Pokemon, it can only be obtained one of two ways. Once you have the National Pokedex, Eevee can be found after defeating the Elite Four or by hunting in the Pokemon Mansion.
Max out Eevee's Happiness Index by feeding it berries, vitamins, fresh water, lemonade and soda pop until it cannot accept any more. While fighting, equip Eevee with the Soothe Ball. In Veilstone City, take Eevee to the massage parlor. Once Eevee has its Happiness Index maxed out, a heart will appear next to it.
Cause Eevee to level up once its Happiness Index is maxed, and it will evolve into Umbreon.