Go to the theme folder and find sidebar.php
Delete the following section:
<li><h2><?php _e('About Me'); ?></h2>
<ul>
<li>Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Vestibulum at arcu. Integer et risus. Morbi id tellus. Integer felis. </li>
</ul>
</li>
Another way to do it.....
1. Click on "pages" on your dashboard.
2. Go to "edit" and a list of existing pages comes up.
3. You will see "about" page, hover over it and you will see "edit" comes underneath
4. Click on the "edit" and you will be able to change it.