You can define the possible attachment files through the Attachment Manager in the admin panel.

Attaching files into posts is only possible if you are using the Post reply option. The Quick reply doesn't support attaching files into posts. The menu is intuitive and is displayed after clicking on the [Manage attachments] button from the options. You can upload both from your computer and to download from an Internet location.
You can define the possible attachment files through the Attachment Manager in the admin panel.
