Hope this helps ...
1) Click the "Manage Attachments" button in the "Additional Options" box, which is right below the "Reply to Thread" box (the place where you type in messages when you're making a post).
2) Click on the "Browse..." button in the pop-up box that appears, and go through your computer's folders to find the file you want to upload.
3) Double-click on the file. Do the same for each additional file. You can choose up to five files.
4) Click the "Upload" button to attach the file(s) to your post. If they exceed the upload limit you'll get a warning and you won't be able to upload them, so make sure they don't.
5) Close the window.