You need to host your own images I think. Have you a website? Or know someone with one. Eg Wordpress: Just upload image to wordpress media library. Then click on the image in the library. Look for the file url. Copy and paste that into the article image box. Thats it.
Discussion
Ah. I did see pulling from a url as an option. Yakihonne says you have the ability to add from gallery but I can't get the function to work unfortunately. I'll keep persisting. 🤙