Here's how to post an image from Flickr.
Go to the image you want to share, and click on the right curved arrow in the lower right corner.
A new window will appear with choices for "Share", "Embed", "Email", and "BBCode". Click on "BBCode" and then select the size of the image you want to share. The text needed to share the image will be in the text window.
Highlight the entire line of text and paste where you want the image to appear. Don't bother with the image tags, as they are already in the link you copied.
This is what the link you copy and paste will look like. It will be different for each image, but will have the same format:
[url=https://flic.kr/p/2kVwH9d][img]https://live.staticflickr.com/65535/51145237184_98d2d71436_c.jpg[/img][/url][url=https://flic.kr/p/2kVwH9d]0420211636_HDR[/url] by [url=https://www.flickr.com/photos/192879473@N04/]Richard Montemarano[/url], on Flickr