First you need two Eevees

In your Leafgreen (If you have one) breed with a ditto so you can get loads of Eevees. Now you need the Eevee to be Level 30 and over so it can learn Bite!!

Trade it to your Emerald and go to Lilycove City. Get a few Irons and Proteins and the rest of that stuff. Give them to your Eevees. Go to Pallet Town and check the time. If it says "AM you get a Umbreon. If it said "PM you get a Espeon. Go to MT.Pyre and go to the very top were that UGLY old man is go to your Right so you can train your Eevees. Train them Until you PP of Bite is gone . Go to Verdanturf and go to the left of Wallys House and you see a women with a Pikachu. Talk to her but keep one of your Eevees in the first slot. Go Back to Lilycove and train again and again but give your Eevees Protein and the rest of those things.

Good Luck!!