the pokeathlon and some other places i think hopfully this helped :D
You need a Eevee and a water stone use the water stone on eevee! Simples!
use a thunder stone
Use a thunder stone on an eevee
Eelektrik, Pikachu and Eevee are the Pokémon that can evolve once you use a Thunder Stone on them.
you use a fire stone on eevee to evolve it into flareon thunder stone = jolton water stone = vaporeon full happenes in day you get espeon night time you get umbreonYou cannot evolve an Eevee into a Glaceon in Pokémon HeartGold, you would have to trade it to either Pokémon Diamond, Pokémon Pearl or Pokémon Platinum and evolve it into a Glaceon there and then trade it back to HeartGold.
use a thunder stone on eevee
Use a thunder stone
It depends when eevee will evolve. Eevee can evolve at any level if you use one of the stones (fire, water and thunder) or, you have to use eevee in battles so it becomes freindlier (use soothe bell as it will help it work faster). My guess that eevee will evolve around 35-50.
Use Thunder Stone to get JolteonUse Fire Stone to get FlareonUse Water Stone to get Vaporeon
Use this chart for SOME of Eevee's evolutions. Eevee+water stone=Vaporeon(water type) Eevee+thunder stone=Jolteon(electric type) EEVEE+FIRE STONE=FLAREON(FIRE TYPE)
if u have an eevee use a thunder stone to evolve it into a jolteon
Eevee can only evolve into Vaporeon with the use of a Water Stone, Jolteon with the use of a Thunder Stone or Flareon with the use of a Fire Stone in Pokémon FireRed and LeafGreen, it cannot evolve into Espeon or Umbreon because there are no day or night functions in FireRed or LeafGreen.