1. Open the reply panel to a Madabout thread or start a new one.
2. Then open a new window and go to the picture on Flickr that you want to show.
3. Just above the photo in Flickr on the left you'll see a small box with a Facebook, twitter symbols plus a little down arrow.
4. Click on the down arrow and you should see a link to "Grab the HTML/BBCode"
5. Make sure "BBCode" is selected and then right click on the code shown in the box. After right clicking, select 'Copy' from the drop down menu.
6. Then switch back to your Madabout window. Right click again in the thread and select 'paste'.
Then finish your update in the thread and select preview when you should see how the photo will look. You can select different size pictures from Flickr if its too small or large.
Its easier to do than write...

Here is a photo I found today...
Marlin Roadster on Ham Mill by Mamod & Moggy Minor!, on Flickr 