How do you "co-author" something? sorry if im being an idiot. Dont hate me.

So i've seen fanfics written by two people and i was wondering how you do that? If you could please help me that would be amazing. Thanks! Peaceskies!

Sometimes, one person writes one chapter an then anther person writes the other. Or they each are on charge of a POV, that I what I'm doing with Detonation Kid

If you mean how to add someone else as an author, create a story, go to the 'authors' button (it's one of the yellow ones by the chapter and edit buttons) And type in the author you want and an invitation will be sent to them.