Hello,
Thank you for contacting Rank Math support.
You need to download an add-on plugin to use the Google Instant Indexing feature. Please read more here: https://rankmath.com/blog/google-indexing-api/
Thank you for choosing Rank Math
What is an add-on plugin? Is that the name of the plugin, or is it something different?
Hello,
You will need to download the Instant Indexing plugin mentioned in our guide

Please follow the steps we have shared previously to setup the plugin in your WordPress.
Looking forward to helping you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.