You can't upload an image to the itch.io community forums. You'll have to host it elsewhere (as a screenshot on your game page for example) and paste just the link here. Press Enter and the editor will auto-embed it.
Also, your game appears to be Flash, not HTML5. Pick the right option under "Kind of project", and upload the .swf. Failing that, make a zip file of both the .swf and a file called "index.html", containing the embed code, and upload the whole thing as a HTML game.
Last but not least, when posting here you might want to write a few words about the game. Is it your first? What will it be about? Did you make the art? So far it looks more like a tech demo. And you really need to work on the grammar/spelling. :)