Go to Shopping Mall Nine on Route 9 (Left of Opelucid City)
On the first floor on the right hand side, there is a doorway to the basement. Enter
Interact with any of those boxes while Rotom is in your party.
Select appliance that corresponds with the type you want from the list
When it does not possess an appliance, it is Normal Rotom, and is Electric/Ghost
When it possesses a microwave oven it becomes Heat Rotom, and is
Electric/Fire
When it possesses a washing machine it becomes Wash Rotom, and is
Electric/Water
When it possesses a refrigerator it becomes Frost Rotom, and is
Electric/Ice
When it possesses a rotary fan it becomes Fan Rotom, and is
Electric/Flying
When it possesses a lawn mower it becomes Mow Rotom, and is
Electric/Grass.
Hope this Helps \m/o_o \m/