Scroll down to the Item Link section. Don't click on any of the Item Link check boxes or radio buttons. Click the browse button next to the "A File" and navigate to the SWF file you created. It's in the same folder as the file you saved previously.

Now click Submit. Hemingway will upload the SWF file, but not link to it. The link is provided by the HTML you pasted into the Description Text file.

Build your site and VOILA!!!