im sorry but i had a total brain collapse or something and FORGET HOW ITS DONE! Could someone simply answer this for me? i would appreciate it :D Thanks! OH WAIT also, is it possible to get more than one eevee without trading on crystal?
for espeon you make eevee really happy then train it at daytime for umbreon make eevee really happy and train it at night time.
To add onto what invisible-chan said, to bring up the happiness of the Eevee, you level it up, train it where you have caught/hatched it, along with going to the Two Haircut brothers. You do that by going underground in Goldenrod (in case you have not remembered), and go to whatever brother is there. SAVE (for reason ahead), then speak to the brother. You want to save, because you want to have your Eevee say that it was delighted. You'll get the most happiness if it says that. :] (Especially if it's the younger brother, as you get a whopping ten happiness points for your Eevee. ^_^)
Hope that helped! :D