First, you need to go to the District of Hope that is in south of the Hospital of Hope, then enter the Pokemon Hospital and talk to the receptionist for an appointment. Once it is done, just go to right room to have your PK's IV modified by the nurse, and that it.
Note: It only changes one you mon's IV per apppointment, so you will need to come multiple times to get all IV's to be perfected. (As I quoted before, I would take a Ditto and perfect it's IV's, then have it hold a Destiny Knot when breeding) .
Good luck.