what pokesav is, it is a program used to hack pokemon, much like action replay, but more advanced. You can hack whatever pokemon you want, ie making a keldeo spawn on route 4. You can hack stats, evs, shininess, and just about anything you can imagine. i tried to attach a link and test it, but it says its outdated, so just google pokesav. its the first link.
i dont use it so sorry i am unsure how to use it.