I can't make the app post an image in the text on my phone. There seems to be no copy and paste function that has the actual URL.

But from my laptop, using https://www.flickr.com/ , it couldn't be easier. From that main page, I go to My Photostream. Uploading photos is an easy one step. Newest uploads are first on the page.

From My Photostream page, I click a photo and this is what I see:

Click the Arrow/Share icon in the lower right. A window opens with 4 options - click BBC code, it comes up highlighted. Copy, that's it. Go to the spot in the text you want to paste the image, and paste.

[url=https://flic.kr/p/Gm8KCi][/url][url=https://flic.kr/p/Gm8KCi]Sterring cable block mounted below2 (1 of 1)[/url] by [url=https://www.flickr.com/photos/131670316@N07/]Tom Young[/url], on Flickr

It will leave the script outside of the img boxes. I delete that.