how do I add a signature to my posts?

I see a button when I post here that is labelled, "Include Signature
Include your profile signature."

Where do I fill out what my signature is?

I looked on my profile page and couldn't find anything.

I haven't heard differently, but last I heard a signature is not a current feature. Including one is though

Oh. OK.

I was just about to ask the same question. :confused