There are some things you have to keep in mind:
- you have to store articles somewhere - database needed. Read some tutorial on MySql if you haven't yet (replace MySql with the database of your preference if you already use one).
- Submission of articles and processing of forms - you've got some examples in what you linked to. Do the same - echo a form for submision and supply some processing for an article. If you don't know what all that code means, I strongly recomend reading some tutorials on processing forms in php.
- prior to echoing form and processing, check if the user is logged in and has necessary permissions to post articles ($session->userlevel from your example).
- displaying articles is straightforward - read them from database (see point one, if you don't know how to).
If you have some question about details , don't hesitate to ask.
