Some contributors have been reporting a problem in uploading attachments in their posts because of missing upload button.

This is a known issue related to the browser your are using and some missing browser components.

But - there is an easy workaround:
  1. Navigate to settings on the right side of the top menu, click there.
    This will take you to your user control panel.
  2. On the left menu you will see "My settings" -> "General settings"
  3. Click on "General settings" and scroll down until "Miscellaneous Options"
  4. In the lower part, in set the "Enhanced Attachment Uploading" to OFF
  5. Now return to your post -> attachments and you should be able to select files and upload them.