In An Unfamiliar Land Walkthrough - Pokemon Legends: Arceus
Follow Professor Laventon and obtain the Arc phone.
Professor Laventon is trying to catch a Pokemon. Head over there and help him.
To catch Pokemon, you will need Pokeballs, he will give you 50 Pokeballs.
Learn how to use Poke Balls to catch the cute little Cyndaquil, Oshawott and Rowlet.
Follow the professor after catching Pokemon.
Professor Leventon will keep showing you the village.
Cross the bridge from the castle. Turn left and head to the wallflower. Professor Laventon is there.
Go to bed.
Go to the Galaxy Team headquarters and talk to Captain Cyllene for your trial.
The mission will be over after Cylleen gives you your first task.