One of the biggest new features to Ultimate Team in FIFA 21 is the introduction of co-op play. This means that not only can you compete against friends in squad battles, but you can now team up to play together to earn rewards.
When teamed in a lobby, you can play in the Division Rivals mode together as well as squad battles, rivals matches, and friendlies, with objectives that are aimed at co-op players to bring in extra XP towards both your Season passes or receive coins and packs.
That said, there’s no option on the menu to actually join together with your friends. Instead, the way in which you team up is on the main Ultimate Team menu. While there, press the right trigger button on your controller, and the profile menu in the bottom right of the screen will appear. In this menu, you should see that you can invite your co-op friend to a lobby with the Options/Start button.
Once you have found the friend you want to invite and have joined a lobby, you can then go to one of the co-op enabled modes and join the queue as a duo, with the invitee player’s team used. You and your duo partner may be required to play your Division Rivals placement matches first if you intend on going into the ranked modes together, but once these are complete, you can start earning your rewards together.
You should be able to play Squad Battles, Rivals, and Friendly matches without completing any prerequisites, so simply team up and start playing to begin ascending the ranks throughout the game.