ok so basically every time you kill a pokemon you get an ev point based on the pokemon you killed. after you get 4 you get 1 stat point depending on the pokemon you killed. you can alter this to make your pokemon better, hence ev training.
to do this you want the following
pokerus (ill give it to you if you dont have it)
power weight gives you four hp evs or 1 hp point
power anklet 4 speed ev or 1 spe point
power bracer 4 atk ev
power lens 4 spatk
power band 4 spdef
power belt 4 def
you can only have 255 evs in 1 stat however 4 is not divisible by 255 so you wanna go for 252
you can max out 2 stats and put 4 evs in one other stat
with the pokerus plus a power item depending on the pokemon you can get 10 evs
meaning you only need to kill (about) 25 pokemon to max the stat
any more questions please ask
i was new to this too but i didnt have anyone to help me out
so feel free to pm me