There are several ways to skin that cat.

The easiest way is usually to check what others have done. In this case, robthebold's post contains the picture embedded, so just click "Quote & Reply" to his post and see how he had done it.

The crucial bit is the URL:
Using that URL to embed the picture, I get this:



Another way is to follow your own link to the Flickr page. It is not entirely obvious how to get the link to the picture, but in the bottom right corner is the "Share" button. That pops up a window with multiple ways of sharing. The useful one is the "Embed" option. This gives you the following, veeeeeery long and unwieldy script:

You need to inspect it and find the relevant part, which is this:
...which happens to be the same as the first one and produces the same result:



Hope this helps,
pichlo