Hi,
For adding category to your blog list and single threat you have to customize the dellow_posted_on function which is define under theme inc/template-tags.php file.
You can replce your function with these..
function dellow_posted_on() {
$time_string = '<time class="entry-date published" datetime="%1$s">%2$s</time>';
if ( get_the_time( 'U' ) !== get_the_modified_time( 'U' ) )
$time_string .= '<time class="updated" datetime="%3$s">%4$s</time>';
$time_string = sprintf( $time_string,
esc_attr( get_the_date( 'c' ) ),
esc_html( get_the_date() ),
esc_attr( get_the_modified_date( 'c' ) ),
esc_html( get_the_modified_date() )
);
printf( __( '<span class="posted-on"><i class="icon-time"> </i> %1$s</span> <span class="byline"> <i class="icon-user"> </i> %2$s</span><span >%3$s </span>', 'dellow' ),
sprintf( '<a href="%1$s" rel="bookmark">%2$s</a>',
esc_url( get_permalink() ),
$time_string
),
sprintf( '<span class="author vcard"><a class="url fn n" href="%1$s">%2$s</a></span>',
esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) ),
esc_html( get_the_author() )
),
sprintf( ' | <span class="cat ">'.get_the_category_list( _x( ',' ) ).'</span>')
);
}
I think it will work for you. Check it..