Simply go to the "reply to message" screen (which you are taken to everytime you want to reply). A tad under the large message box is a seperate section of other options. In there is an attachments field. Simply click on the "manage attachments" button and upload
For more detail, you can check the Oddworld Forums FAQ section on attachments:
http://www.oddworldforums.net/faq.ph...chment_explain
Alcar...