Question: how to play co op in pokemon sword?
Answer: From the game, press 'Y' to access the trading (or 'Y-Comm' menu). In order to trade with a friend, you'll need to access the 'Link Trade' option, and then set a Link Code. You'll need to give this code to a friend and, once they've inputted it, you'll be able to connect to each other to trade Pokémon.