You can do it one of two solid ways, assuming you have pokemon platinum.
Way 1: Chain breed, eventually the rng (random number generator) will give you a shiny baby. (you can also read a guide on how to manipulate the rng so the baby will be guarenteed to be shiny, just google search, shiny pokemon rng guide or something similar)
Way 2: After you beat the E4 and have aquired the pokerader from Lucas/Dawn at Rowan's Lab. Occasionally the randomly encountered pokemon at the trophy garden will be eevee, (talk to the mansion owner and he'll tell you what the daily pokemon is, just come back everyday till its eevee) Once you encounter an eevee in the garden use the pokerader and some grass will shake, move onto the shaking grass and there is a good chance it will be another eevee, everytime you successfully hit an eevee, the chances of the next shaking grass being an eevee go down and the chances of it being shiny go up. There are guides on this forum on to raise the success rate.
I myself have caught 3 shiny eevees in about 11 hours using way 2.
And thats not a silly question its a very intellegent question. What Eevee fan wouldn't want to know. Happy hunting and good luck!