You can click on the "manage attachements" button at the end of the page. If you did not see this button, then you need to click on the button that says "Additional Options", this AO button will pop up the "manage attachements" field for you. A new window will be pop up after clicking the "mamage attachements", which allowing you to upload for picture/files. Then click on the Browse button, and select the picture in "my Documents/My Pictures" directory that you want to imbed it in your reply. Then click on the button that say "Upload" -
Hope this will help.