I don't see where a user can simply upload a file to a page. How does one do this, and how does it get set up?

If you have permission to upload files (see ACL) you can use the add images button to upload files (when you are editing the page). Only certain filetypes are allowed to be uploaded. This is configured through the mime.conf file.

The upload utility is called the mediamanager. Read about the mediamanager to get more details.

Please note, normal users are not allowed to upload here on www.dokuwiki.org.