When you do a posting, note the buttons in the "vB Code" section (which is under the "Message Icon:" section). First, copy the link to the image, and then press the "IMG" button, which is under the "vB Code" section. Now just paste the link into the window that pops up and press OK.
Alternatively, you could just put the link to the image around an image tag, which corresponds to .
As to the secondary name under your username, this is configured under your "User Control Panel". Simply click the "user cp" button that's under the main banner at the top of every page. Then go to the "profile" section.