Walkthrough
After purchasing the Pokemon Sword & Shield Expansion Pass from the Nintendo Shop, you will earn access to both The Isle of Armor and The Crown Tundra. Immediately after purchasing the DLC Package, an event will occur at the Wedgehurst Train Station. Once you arrive, you will see a Galarian Slowpoke. Soon after, you will meet either Klara or Avery depending on which version of the game you are playing. They will chat with you about The Isle of Armor - which is where you will see these characters once again - before suggesting you capture the Galarian Slowpoke. By doing so, you will be able to evolve it into either Galarian Slowbro when on The Isle of Armor or Galarian Slowking when in The Crown Tundra.
Interactable
Galarian Slowpoke (100%): Level 12