A link to your site is necessary for CSS-related questions.
.postmetadata .meta-author { display: none; }
will do this 🙂
Also make sure to add this in css/theme-style.css, as the default “style.css” is not used by the theme. (It will be in the next revision for easier custom css use and to improve child-theme support.)
I tried both of these but am having no luck. My site is http://verefoster.info with Responsive theme