I'm using markup and for me, it's quite simple but it's easy to make mistakes at first.

In markup, you can mark something as a link by putting [ and ] around it. So in this case, I'm putting [ ] around the url of the image, so the image is the link.

Then I'll just copy the image url as the target of the link within ( ).

It looks something like this:

And as usual, you can click on the image to open it in full size :)