When you are posting, in the top of the toolbar where you are typing your message, there should be a paper clip next to a smiley face.
Click on the paper clip, and another window titled "Manage Attachments" will open, asking you to upload a file, or "browse".
If you click browse, you can select a pic from your computer. After you select your picture, you will have to "upload" it.
Once it's uploaded, if you close that window, and 'preview' your post, you will see you pictures file name under 'additional options', directly below the "reply to thread" box.
Hope this helps.......