You can't put pictures (apart from your avatar, of course!) on AB. You have to get the picture hosted somewhere on the web, then post a link to it.
Start by saving the picture in your email to your hard drive:
Right-click on the picture, select 'Save Image As' (or whatever similar term your browser uses). Navigate to somewhere suitable on your computer (such as 'My Pictures' or, for a temporary location 'Desktop').
(Rename the file if you want to).
Click 'Save'.
Then go to here:
http://www.tinypic.com/
Click 'Browse'.
Navigate to the location of the file you've just saved and double-click on it.
Click 'Upload Now'
Enter the two security words into the box and, again, click, 'Upload Now'
Click in the 'Direct Links for Layout' field, to highlight the URL.
Right-click and select 'Copy'
Go to where you want your link to appear in your CB post.
Right-click and select 'Paste'
Chris