You can post it as your own post and then leave a link in the comments - or, if you like to keep your feed a certain way, i.e. only animal pictures or something like that, and your story doesn't fit there, you can post it in the comments.
Some people do both.
Do you mean the final story? Like which person posts the finished story?
Yes, that. But also, is the story posted as a comment here? Or where?
Yes, you can post the finished link here. You and your partner can both post the finished story, or just one or the other.
You can post it as your own post and then leave a link in the comments - or, if you like to keep your feed a certain way, i.e. only animal pictures or something like that, and your story doesn't fit there, you can post it in the comments.
Some people do both.