When you first view the discussion, it lists the most recent articles in the discussion. On this DBabble server, it is the 50 most recent items, but this may differ on other servers. You can browse through older items by using the page down and page up buttons. Since articles are ordered by date, replies posted to articles may not be on the same page as the original article. In order to view all article headers for a single thread of replies, you can choose the View Entire Thread link which is available when viewing the content of an article.
Any article posted in a discussion can optionally have a file attached to it.
You can download or view an attachment from the bottom of the article content page. However, you can find specific attachments more quickly by clicking on the files link in the discussion window. This will list all attachments posted to the discussion rather than articles, with links to download the file, or to view the article it is attached to. You can post a new article to a discussion by clicking on the Post link at the top of the discussion window. However, if you are wanting to reply to an existing article, you should instead click on the Reply button available from the article content window.