You get the Soothe Bell in the National Park if I remember correctly. I forget exactly where you get it, but I do know that you can get it as soon as you visit it first time. After getting said Bell, just ride around on your Bike mindlessly until your Eevee is happy enough to evolve into Espeon/Umbreon. That's what I did early on in the game to get my Eevee to evolve into an Espeon.