1、修改site-info.php (template-parts/footer/site-info.php),选择合适的位置添加备案信息
<div class="site-info">
	<?php
	if ( function_exists( 'the_privacy_policy_link' ) ) {
		the_privacy_policy_link( '', '<span role="separator" aria-hidden="true"></span>' );
	}
	?>
	<a href="<?php echo esc_url( __( 'https://wordpress.org/', 'twentyseventeen' ) ); ?>" class="imprint">
		<?php
			/* translators: %s: WordPress */
		printf( __( 'Proudly powered by %s', 'twentyseventeen' ), 'WordPress' );
		?>
	</a>
	<?php if(get_option('zh_cn_l10n_icp_num')){?>
	        
	<a href="http://beian.miit.gov.cn/" rel="external nofollow" target="_blank">
	<?php echo get_option('zh_cn_l10n_icp_num');?>
	</a>
	<?php } ?>
</div><!-- .site-info -->
2、修改 /var/www/html/wp-config.php
/**
 * zh_CN本地化设置:启用ICP备案号显示
 *
 * 可在设置→常规中修改。
 * 如需禁用,请移除或注释掉本行。
 */
define('WP_ZH_CN_ICP_NUM', true);