Mistress Cogita says to check Prelude Beach to get one of the Plates.

Go to Jubilife Village

After you have talked to Mistress Cogita about the beginning, during The Researcher of Myths, go to Jubilife Village, and Commander Kamado will meet you when you arrive.

Go to Prelude Beach

Go to Prelude Beach in Jubilife Village and approach Commander Kamado on the pier.

Do Battle

You will battle Kamado's level 65 Golem, level 66 Snorlax, level 65 Heracross, level 65 Braviary, and level 65 Clefable.

Afterward, you get the Fist Plate.

• The Plate of the Lakes
• The Plate of Firespit Island
• The Plate of Moonview Arena
• The Plate of Snowpoint Temple