You can't place images directly onto AB. You have to upload tthem elsewhere and then post a link.
Try this:
Go here:
http://tinypic.com/
Click Browse.
Navigate to the location on your hard drive of a picture you'd like us to see.
Double-click on it.
Click Upload Now
Complete the security thingy (where you have to type something to prove that you're a real human being)
When your picture appears, click on the last of the four links shown, to highlight it.
Right-click and select Copy.
Come to an AB post, right-click and select Paste.