hatch from egg breed in day care evee and ditto
Eevee can not evolve into porygon.
You can get an Eevee from Bill in Goldenrod city.
You can not, you have to go to bill's house in goldenrod city to get a eevee.
Once you get an eevee from Bill. (House in Goldenrod City gives one for free) take it and a ditto to day care. Leave them in there. Soon there will be an egg there. Hatch it to an eevee.
Evolve Eevee, or trade.
Bill will give you an Eevee.
get an eevee and evolve it into a thunderstone
You need a Eevee and a water stone use the water stone on eevee! Simples!
You can find eevee in Celadon City in Kanto as a Game Corner prize.
To evolve the Pokémon Eevee in Pokémon HeartGold and SoulSilver, you can choose either of the two choices described below:Train Eevee in the nighttime when it has max happiness.Train Eevee in the nighttime when it is around a Moon Shard.Steps have nothing to do with the evolution of Eevee.
A water stone
you can find a leaf stone in viridian forest in kanto in heartgold