Tommy Tayler said:
Did you buy the digital version of the game or you just downloaded a pirated version ? The multiplayer doesn't work on the pirated version and the pc community doesn't support piracy so I can't really help you with that but in case you bought the game, then the multiplayer can be accessed from the game menu. The multiplayer of dead island is only co-op, there is no competitive online so you can only play the single player with other players who are at the same game chapter as you.
Oooh, I bought the game. And when I try to join someone who are at the same chapter as me I always get an error.