This will go in functions.php in your theme. This example removes the word "About" from the box title.

Filter Title in Genesis Author Box

/** filter author box that uses user biographical info  **/
add_filter( 'genesis_author_box_title', 'dc_change_authbox_title' );
function dc_change_authbox_title($goodies) {
	$goodies = str_replace("About", "", $goodies);
	return $goodies;
}