Click on the following words:
Go Advanced
Then Manage Attachments
Then click on pic you want to post
Next click Open
Then click Upload
And finally click on the Insert Image Icon
(Yellow icon at top of page)
Another way is to open up a photobucket account. Upload your pics, then copy the address of the pic which should be photobucket.com/blahblahblah.jpg, or something similar. Then put that address in this: