If you would like a Table of Contents in your submission you have to select that checkbox when you write the sub. It is in the same area as locked and the wiki selection title, surprisingly enough, Table of Contents (ToC).
Click that and the ToC is enabled.
On your submission, use the Heading buttons to organize your submission. Currently the only Headings that the ToC will grab are the three largest font sizes. From the dropdown that is the top three. (h1,h2,h3)
Simply organize you content with those three Headings and the ToC will be automatically created in your submission.