I made a story a few months ago and while I have completed over four chapters (with pictures) I could never figure out how to post the second chapter, because its like a thread I wasn't able to understand how it worked.

The story is on this website under Sims 2 Stories, because I would rather update it before anyone reads the one chapter I have, I won't bother posting the link.

I think it's enough to add a new title to the post, and it will automatically save as a new chapter. I checked one of my old stories on there, and I couldn't find anything different from a regular post, aside from the title.

But I'm asking what am I clicking to be able to do that. I only see the reply and edit options at the bottom of the first chapter and that looks like what you use to either quote the story or reply to someone else's comments

You need to be in "Advanced" mode. Then you get both the reply/message box AND a (blank) title box. Fill in the title with your new chapter title and it will automagically appear in the Table of Contents for the story

I replied to your PM