1) Log in.
2) Mouse over where it says "Submit" near the top of the screen, then in the menu that pops up, click "Submit Art."
3) On the page that comes up, enter your artwork title and decide which category your artwork fits under. Where it says "Which File?", click the "Add a File..." button to upload your artwork. Write comments, keywords, and choose maturity settings below that.
4) Click "Submit."