There are two ways 1. You raise the Eevee you obtained from BEBE, maximize it's happiness then evolve it at night ( must be happy to evolve, and must be at night ). 2. There is a Pokemon Collector, trainer between the marsh and the water on route 212 that has one, just battle him and Umbreon will show up on your pokedex. If you want an Umbreon and you've already evolved the one that BEBE gave you it's okay, once you've finished the pokedex from Giratina down you can find some in the trophy garden.OR, you can put your eevee--evolved into whatever form--into the daycare center with a ditto. It will produce an egg which hatches into eevee; then follow the instructions in the above #2