After the introductory cutscenes and choosing your gender and name, you'll find yourself in Ringtown. Your first task is to report to Professor Hastings at the Ranger Union headquarters. Head north through Ringtown. You'll encounter a few NPCs who will give you basic tips. Once you reach the large building with the Ranger Union emblem, enter it.
Inside, proceed to the main office area. Professor Hastings will greet you and explain the basics of being a Pokémon Ranger. He'll also introduce you to your Partner Pokémon, either Minun or Plusle, depending on your choice. This initial interaction is crucial for understanding your role and the game's premise. Pay attention to the dialogue as it sets the stage for your entire adventure.