Everything is better with friends, and this applies to Pokemon Brilliant Diamond and Brilliant Pearl. If you want to play with your friends, fight together, and generally enjoy games, there are a few things you need to know.
First, you'll need a Nintendo Switch Online membership to play online and access all of these features. Battles with other coaches, trading and all that good stuff will require online registration.
After that, you'll need to go to any Pokémon center and go down the red escalator. This will take you to the Union Hall. Talk to the people behind the counter and they will tell you that you are in the Pokémon Global Club.
They will ask you if you want to enter and will give you four options:
- Yup
- Yes, with my group
- Yes, with a link code
- No thanks
Choose the option that's right for you and then you can enter the Global Room. If you choose a Link code, give it to your friends and they can use it to gain access and they can fight and trade with you.
Note that for exchanges, you will need to have completed the first gym before you can trade with other players.