@arundhati1213
We do have some documentation that you might find useful to add custom meta tag on your post/page:
https://developer.yoast.com/blog/yoast-seo-14-0-adding-metadata/
https://developer.yoast.com/customization/apis/metadata-api
Unfortunately, there’s a difference between the support we can offer and the level of programming needed to change (core) features of our plugin. Since we don’t want to take the risk that we break your website by suggesting incorrect or incomplete code, we cannot advise you on how to make such changes. And even though we cannot be of any assistance, you’re completely free to change anything in the plugin to better suit your needs.
We highly recommend checking out available freelance WordPress developers for development & consultancy.