IN route 9 shopping mall, there is a door on the right side of the wall on the first floor. Go in, and you will see many boxes. press A in front of one of them to change Rotom's form.
Lawnmower = Rotom-Mow = grs/ele = Leaf-storm
Mircowave = Rotom-Heat = ele/heat = Overheat
Washing machine = Rotom-Wash = wtr/ele = Hydro-pump
Electric fan = Rotom-Fan = ele/fly = Air-slash
Refrigerator = Rotom-Freeze = ele/ice = Blizzard
Recall = Rotom = ght/ele = Thunder-shock