A little more information that might help. If you want to use the "Optional Image URL:" text box below you need to dig out the part of the link starting with https and ending in .jpg. in the example below, copy https://c5.staticflickr.com/9/8565/28911270836_49137ae3cc_b.jpg into the image box below. Remember you need to remove the http : // that is pre-populated in the Optional Image text box.
[url=https://flic.kr/p/L3MPyQ][ img]https://c5.staticflickr.com/9/8565/28911270836_49137ae3cc_b.jpg[ /img][/url][ url=https://flic.kr/p/L3MPyQ]DSC_1203[/url] by [ url=https://www.flickr.com/photos/144419195@N03/]Darcy Craig[/url], on Flickr