I must be a dunce because my links aren't working.
If you click on the tiny icon above the input box when you're creating a post (4th from left; might be a tree?) it brings up a box prompting you to enter the URL. That should be something starting with [b:84008b92bd]http:[i:84008b92bd][/i:84008b92bd]//[/b:84008b92bd] and ending with .jpg (probably).
On the flickr photo page, click: Share > Grab the HTML/BBCode > BBCode, then copy & paste that code into your post here.
[url=http://www.flickr.com/photos/jennyhill/44438129/]sj104_0448[/url] by [url=http://www.flickr.com/people/jennyhill/]JennyHill[/url], on Flickr
Aww, don't they all look so young