You've done all the hard work of getting the image into flickr.
I went to the flickr page, chose download, then all sizes, then original size,
then right click on the image to get its properties (its URL).
Copied the properties URL filename.jpg, pasted it into the PM "image add" field to finish up.
The key to it, is to make sure the link (URL) ends with extension *.jpg
In this case, it was "https://live.staticflickr.com/65535/32762690017_8e6b5bafc6_o.jpg"
and the PM "image add" icon will add the "[img]" tokens to front and back of that URL.
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.... rule #9 ....