Hi @edwinfu,
To do that, please install and activate the child theme. If you do not have the child theme installed yet, you can download it from here. Once you have it installed and activated, please login through FTP then go to wp-content/themes/x-child then go back to wp-content/themes/x/framework/legacy/cranium/headers/views/renew/ then copy the file _landmark-header.php and place it to wp-content/themes/x-child/framework/legacy/cranium/headers/views/renew/ then edit the file and replace the current file content to:
<?php
// =============================================================================
// VIEWS/RENEW/_LANDMARK-HEADER.PHP
// -----------------------------------------------------------------------------
// Handles content output of large headers for key pages such as the blog or
// search results.
// =============================================================================
$disable_page_title = get_post_meta( get_the_ID(), '_x_entry_disable_page_title', true );
$breadcrumbs = x_get_option( 'x_breadcrumb_display' );
?>
<?php if ( ! x_is_blank( 1 ) && ! x_is_blank( 2 ) && ! x_is_blank( 4 ) && ! x_is_blank( 5 ) ) : ?>
<?php if ( is_page() && $disable_page_title == 'on' ) : ?>
<?php else : ?>
<header class="x-header-landmark">
<div class="x-container max width">
<div class="x-landmark-breadcrumbs-wrap">
<div class="x-landmark">
<?php if ( x_is_shop() || x_is_product() ) : ?>
<h1 class="h-landmark"><span><?php echo x_get_option( 'x_renew_shop_title' ); ?></span></h1>
<?php elseif ( x_is_bbpress() ) : ?>
<h1 class="h-landmark"><span><?php echo get_the_title(); ?></span></h1>
<?php elseif ( x_is_buddypress() ) : ?>
<?php if ( x_buddypress_is_component_with_landmark_header() ) : ?>
<h1 class="h-landmark"><span><?php echo x_buddypress_get_the_title(); ?></span></h1>
<?php endif; ?>
<?php elseif ( is_page() ) : ?>
<h1 class="h-landmark entry-title"><span><?php the_title(); ?></span></h1>
<?php elseif ( is_home() || is_single() ) : ?>
<?php if ( x_is_portfolio_item() ) : ?>
<h1 class="h-landmark"><span><?php echo x_get_parent_portfolio_title(); ?></span></h1>
<?php else : ?>
<h1 class="h-landmark"><span><?php echo get_the_title(); ?></span></h1>
<?php endif; ?>
<?php elseif ( is_search() ) : ?>
<h1 class="h-landmark"><span><?php _e( 'Search Results', '__x__' ); ?></span></h1>
<?php elseif ( is_category() || x_is_portfolio_category() || x_is_product_category() ) : ?>
<?php
$meta = x_get_taxonomy_meta();
$title = ( $meta['archive-title'] != '' ) ? $meta['archive-title'] : __( 'Category Archive', '__x__' );
?>
<h1 class="h-landmark"><span><?php echo $title; ?></span></h1>
<?php elseif ( is_tag() || x_is_portfolio_tag() || x_is_product_tag() ) : ?>
<?php
$meta = x_get_taxonomy_meta();
$title = ( $meta['archive-title'] != '' ) ? $meta['archive-title'] : __( 'Tag Archive', '__x__' );
?>
<h1 class="h-landmark"><span><?php echo $title ?></span></h1>
<?php elseif ( is_404() ) : ?>
<h1 class="h-landmark"><span><?php _e( 'Oops!', '__x__' ); ?></span></h1>
<?php elseif ( is_year() ) : ?>
<h1 class="h-landmark"><span><?php _e( 'Post Archive by Year', '__x__' ); ?></span></h1>
<?php elseif ( is_month() ) : ?>
<h1 class="h-landmark"><span><?php _e( 'Post Archive by Month', '__x__' ); ?></span></h1>
<?php elseif ( is_day() ) : ?>
<h1 class="h-landmark"><span><?php _e( 'Post Archive by Day', '__x__' ); ?></span></h1>
<?php elseif ( x_is_portfolio() ) : ?>
<h1 class="h-landmark"><span><?php the_title(); ?></span></h1>
<?php endif; ?>
</div>
<?php if ( $breadcrumbs == '1' ) : ?>
<?php if ( ! is_front_page() && ! x_is_portfolio() ) : ?>
<div class="x-breadcrumbs-wrap">
<?php x_breadcrumbs(); ?>
</div>
<?php endif; ?>
<?php endif; ?>
<?php if ( x_is_portfolio() ) : ?>
<div class="x-breadcrumbs-wrap">
<?php x_portfolio_filters(); ?>
</div>
<?php endif; ?>
</div>
</div>
</header>
<?php endif; ?>
<?php endif; ?>
Then add this code in X > Theme Options > CSS:
.single-post .entry-title {
display: none;
}
Kindly note that since this is a custom code that changes the default behavior/display of the theme, you will be responsible to maintain or update the code in case you require further changes or if the code stops working in future updates. If you are uncertain how to proceed, it would be best to get in touch with a developer.
Hope this helps.