After the "message" field there's an "attachments" area. Just "add file" and you should get a pop up box allowing you to browse your files and select the evp you wish to post.
If the link doesn't provide a popup box for browsing your folders, maybe try a different browser? If that doesn't work, try contacting crystalcross through the messaging system, he's usually very helpful with the technical details.
Good luck, and welcome to GnH!
