How do you find captain stern and give him the scanner?

To find Captain Stern, you typically need to progress through the storyline in the game, often starting from a specific location such as a Pokémon Center or a nearby town. Once you locate him, usually in a place like the Stern Shipyard, approach him and engage in conversation. During this interaction, you can present him with the scanner, which is often obtained through a quest or after defeating certain trainers. Make sure to follow the quest prompts to ensure you have the scanner ready for the exchange.