First you have to obtain an Eevee from Bill in Goldenrod city after talking to him in Ecutrek. Then train ,battle , groom the eevee until it is fully happy. (There is a lady who will indicate when Eevee is really happy in goldenrod ( She is in the opposite side of Bills house)). Then level Eevee up during the day time and it will become and Espeon. However if you level it up during night time it will become an Umbreon.
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Pikachu into Raichu, and Eevee into Jolteon. I don't recommend evolving Eevee into Jolteon. Espeon is way better.
train your eevee in the afternoon
In Pokemon soul silver you get eevee from goldenrod city, go to bills house talk to him (after you've met him in Ecruteak) and he will give you a eevee, level it up with max happiness during the day and it will evolve into espeon.
sorry you have to trade it to Pokemon soul silver
Zorua is a 5th generation Pokemon it is not available in soul silver.