First of all, you need to confirm whether your domain name is registered successfully
After the domain name registration is completed
You just need to open wordpress background (http://(domain name)/wp-admin)
After entering, find the appearance and open the theme file editor
Find the footer.php theme footer
Just insert these two lines of code into the middle of the footer - remember to modify the record number
</div><!-- .wrap --><a href="https://beian.miit.gov.cn/" rel="external nofollow" target="_blank">(备案号)</a></footer><!-- #colophon -->