Basically, how this works is that each person is only able to say one word at a time to make a story. You may use any punctuation you want.

I saw someone edited their message, I'll let that one slip. But try not to edit your message!

Here is a short example with a story that's literally one sentence:
(P stands for player)

P1: (START OF STORY) I
P2: like
P1: pineapples. (END OF STORY)

Let me start!

(START OF STORY) Once