In Valheim, there is both a single-player mode and co-op. Playing together with friends adds excitement and joy from exploring the vast land of the Vikings. However, since the game is in early access, many technical issues have yet to be resolved in a way that is intuitive. Check out our guide if you want to learn how to play Valheim in co-op.
You should start by creating a character. Logically, characters should be had by everyone with whom you plan to play. Note that one of you should also create a server. This process is not simple and may take some time, so you need to prepare for joint play in advance. You can immediately connect to one of the ready servers in the list, which can save a lot of time, but besides you and your friends, there will be unfamiliar players in the game.
Then, make sure you have created a world. The game itself will offer you to choose a name for the world and show you the seed identifier, so you are unlikely to miss this step. You don't need the seed, focus on the world. This is important because the name needs to be specified in the server settings, of course, if you are going to create it. So, come up with something individual and memorable, so your friends can easily find it in the search for worlds.
Add a password to the server and select the Community Server option. Note that the password is not just protection from outside players. Without it, the server will not work properly, at least some players have mentioned this issue.
As soon as everything is done, you will see the opening cinematic where a raven will transfer you into the game, and then your friend can find the server in the community servers list and enter the password to join.
Thus, the order of your actions will be approximately as follows: