You can't. Since it is modified after the original Red and Blue versions, it only has the evolutions present in Red and Blue: Flareon (using a fire stone), Jolteon (thunder stone), and Vaporeon (water stone).
Evolve it from eevee
Ive hear my friends say that in Pokemon yellow you can evolve eevee in a espeon with a moon stone
You can't. It evolves by the time of day. Since there isn't a clock, eevee won't evolve into espeon OR umbreon.
give it a thunderstone
Max out Eevee's happiness during the day. ~KKMG1
You will get an eevee egg. That you can evolve into an eevee or the other eevee evolutions.
espeon evolves from Eevee fromHappiness during the day, or when around a Sun Shard
Evolve Eevee during the day
In Pokémon Flora Sky, to evolve Eevee into Espeon, you need to level up Eevee while it has high friendship with you. Make sure Eevee's friendship level is at least 220, and then level it up during the day. After meeting these conditions, Eevee will evolve into Espeon.
When Eevee loves you, level it up in the Morning.
You can use moon stone i think
You evolve an Eevee into and Espeon by raising it to max happiness. Pokemon gain happiness when you give them massages (in Goldenrod underground and Blue's sister.) It will take a while to reach max happiness. Then you level it up in the day. It will evolve into Espeon.