Well,the little icon that looks like a piece of paper with shapes
does it. It's above your text area.
Just click that,and it will ask you to type in URL of that image.
Once you've done that,just click ok,and it should pop up.
Some of them won't show up,and that's 'cause this site can't link
to the site with the image. But most of the time it works. And of course, always preview your post first when posting an image.
I look everywhere for good pics,and pick the ones I like