How to Put ‘Noindex’ Meta Tag on WordPress Page Without Using a Plugin

I used the Yoast SEO plugin to add a ‘noindex’ meta tag to some pages on my website. However, when I removed the Yoast SEO plugin, the ‘noindex’ tag was also removed. How can I directly edit the HTML of each page and add the ‘noindex’ tag without relying on the Yoast SEO plugin?