Things You'll Need
Instructions
Travel to Eterna City. Use your Dowsing Machine PokeTech app to locate the Draco Plate, hidden behind a statue. This Plate switches Arceus to a Dragon-type Pokemon.
Exit the city, heading into the Eterna Forest. Go to the Old Chateau and enter the back room. Use the Dowsing Machine to find the Dread Plate hidden in this room. This plate switches Arceus to a Dark Pokemon. Head outside of Old Chateau and search the immediate area to find the Insect Plate.
Travel to Oreburg City and make your way to the Oreburg Gate. Enter the basement and cross the patch of water. Use "Strength" to push the boulder aside that's blocking your path. Near the boulder you'll find the Earth Plate, switching Arceus to a Ground Pokemon.
Go to Stark Mountain and use the Dowsing Machine near the far left wall. Here, you'll find the Flame Plate, switching Arceus to a Fire Pokemon. Make your way to Route 215. Near the Route's entrance, use "Cut" on a tree blocking the path. Hidden behind the tree, you'll find the Fist Plate, making Arceus a Fighting Pokemon.
Travel to Route 217 and go to the Route's west end. Go to the house and, if you haven't already, pick up the HM08 sitting outside. Talk to the man inside and he'll give you the Icicle Plate, making Arceus an Ice-type Pokemon.
Go to Iron Island, either using "Surf" or "Fly" to get there. Use your Dowsing Machine to investigate the lowered sections of the floor. One of the lowered sections contains the Iron Plate, switching Arceus to a Steel Pokemon.
Move to Route 210 and use "Swim" to get downstream. Go up the waterfall and use the Dowsing Machine next to the empty land plot to find the Meadow Plate. This one makes Arceus a Grass Pokemon.
Navigate to Solaceon City and head to the Solaceon Ruins. Use the Dowsing Machine within the ruins to find the Mind Plate, making Arceus a Psychic-type Pokemon. Head to Victory Road's exit and use the Dowsing Machine to find the Sky Plate. This Plate make's Arceus a Flying Pokemon.
Go to Route 220's beach and find two girls in bikinis. South of these girls, you'll find the Splash Plate, making Arceus a Water Pokemon.
Travel to Hearthome City and enter the PokeCenter. Use the PC to change your Pokemon. For the Spooky Plate, you need to enter Amity Square, where only 11 specific Pokemon may go. Equip any combination of Pikachu, Shroomish, Pachirisu, Psyduck, Skitty, Torchic, Jigglypuff, Clefairy, Driftloon, Happiny or Buneary. Enter Amity Square and find the Spooky Plate to the right of the area's building. This Plate changes Arceus into a Ghost Pokemon.
Go to the peak of Mt. Cornet. Use the Dowsing Machine to find the Stone Plate, transforming Arceus to a Rock Pokemon. Head to Sunyshore City's Lighthouse. Use the Dowsing Machine right in front of the lighthouse to find the Zap Plate, turning Arceus into an Electric Pokemon.
Head to the Great Marsh near Pastoria City. Travel to the Northeast corner of the marsh and search the trees in this area using the Dowsing Machine. The fourth one from the area's corner contains the Toxic Plate. This Plate transforms Arceus to a Poison Pokemon.