Here is my blockhead-friendly idiot-guide.... it works for me..
Helps to have two tabs open in your browser... the one where the picture is, (flickr), and the one where you're trying to get it, (the text-box that comes up here when you press 'new topic' or 'post reply')
Over here, press the 'img' button above the text-box, which will then appear in the text-box, then click on the other tab in your browser to go to the picture.
right-click on the image you are after.
left-click on 'properties'
left-click on the end of 'Address (URL)' which will scroll to the end of the address, usually 'JPG'
left-click and hold down, move mouse leftwards to highlight entire address
right-click on highlighted address
left-click on 'copy'
Now you can return to the other browser tab.. left-click to bring you back here.
in the text-box, left-click to get the cursor just after the [img] (if it's not there already) once it is there, right-click, and then left-click on 'paste'...
The URL of the image should appear. If it does, left-click on the 'img' button above the text-box again (which now says; '/img' or something like that).. This should then appear after the URL in the text-box..
That's about it... If you press 'preview', you should see your picture.
Yeah I remember 'How?'..