One of the biggest features of Ultimate Team in FIFA 21 is the introduction of the cooperative game. This means that not only can you face friends in team battles, but you can now team up to play together to earn rewards.
When you are in a team in a lobby, you can play together in Rivals Division mode, as well as team battles, rival matches and friendly matches, with goals for cooperative players to bring extra exp to your Two seasonal passes or receive parts and packs.
That said, there is no option in the menu to join your friends. Instead, the way you team team is in the main menu of Ultimate Team. While you are there, tap the right trip button on your controller and the profile menu at the bottom right of the screen will appear. In this menu, you should see that you can invite your friend Coop in a lobby with the Options / Start button.
Once you have found the friend you want to invite and have joined a living room, you can access any of the modes enabled in cooperation and join the duet queue, with the guest player team. used. You and your Duo partner may need to play your division Rivals investment games first if you intend to move together to the classified modes, but once they are finished, you can start winning your rewards together.
You should be able to play team battles, rivals and friendly matches without fulfilling the prerequisites, then simply team and start playing to start climbing the ladder throughout the match.