You still have not yet set the page as a static front page: http://en.support.wordpress.com/pages/front-page/
Once you do, the Showcase page will appear in front. Then, Sticky posts with Featured Images that are at least 750 pixels in width will appear in the slider.
Once you have set the front page to your About page, see this for further details: http://theme.wordpress.com/themes/oxygen/
