Question: pokemon let's go pikachu how to judge?
Answer: Have captured at least 30 species of Pokemon.
Go to Route 11, east of Vermilion City.
Go all the way to the building that connects Route 11 and Route 12 (It's the walkway building that has a guard in it)
Go up the stairs.
Talk to Professor Oak's assistant.
He'll enable Judge in your Pokedex.