Here's how I posted the Lon Chaney pic above.
I found an image of what I was looking for on the web. I saved it to my computer (I used lonchaneyeyes and it saved as a .jpg).
I went to
https://postimages.org/ and clicked Choose Images. I located the image I wanted on my computer and clicked Open. After a moment, a whole bunch of links appear. I always choose the second one, Direct Link, and copy it.
At FR, type in < img src="" width="40%" > and paste in the Direct Link from Post Images, like so:
< img src="https://i.postimg.cc/ZRf4B9ns/lonchaneyeyes.jpg" width="40%" >
Now, I had to put spaces inside the angle brackets, the < and >, so you can see the HTML, but you have to remove the spaces for the image to actually show up. Also, the 40 percent can be any number from 1 to 100. I've found 40% usually works well. The image will be 40% of your whole computer screen. When in Preview, it only shows as 40% of the Preview window, so it will look smaller than it will when you actually post it.
So you end up with this:
Hope that helps!