I must admit to struggling a little to work out the correct process for this.

If you want to insert an image from your Flickr account to a post……

Create your new topic as normal, then in your flickr account, click the ‘share’ icon.

Then you’ll get the following form popup.

 

Make sure you click on Grab the HTML/BBCode (Items highlighted in pink)

Then copy ALL (Ctrl-A, Ctrl-C) text from the yellow highlighted part into your post.

 

Hope that helps