How can I put a png file into the binder?

I take screen shots a lot, which are png files. I want to bookmark them to specific documents. Right now I’m putting them in a file in dropbox before I bookmark them.

That works, but I would prefer to be able to put the png image directly into the project binder and then bookmark it, but I can’t see how to do it. I can’t drag and drop and when I select Import, the png file is greyed out.

The same is true for jpeg files.

Put it in the Research folder, which supports all file types. The Draft folder can only contain text files, so you’d need to copy and paste the image into a text document if you want it there.