Hello,
We apologize for the issue you are facing with setting the Noindex option on your individual posts. To set Noindex for a specific post, you need to edit the post and scroll down to find the Rank Math SEO settings below your post. Look for the Advanced tab in the Rank Math meta box. In the Robots Meta section, you should see the No Index checkbox that you can select to prevent the post from being indexed.
Here’s a visual guide to help you:

If you are using the Gutenberg editor, the process is similar. Edit the post, go to the Advanced tab, and check the No Index box:

For setting Noindex for a specific category, you can use the Bulk Actions feature in the Posts section of your WordPress dashboard. Select the posts you want to set to Noindex, choose Set to noindex from the Bulk Actions dropdown, and then click Apply. This will apply Noindex to all selected posts.

If you’re still having trouble finding these options, please reply to this ticket with your site URL, and a human agent from our support team will assist you further. Thank you for raising this concern!
Sources:
How to Noindex URLs With Rank Math » Rank Math
How to Noindex URLs With Rank Math » Rank Math
How to NoIndex All Posts in a Category » Rank Math
Hello,
I can´t find those options. Is this only for pro users?
Hello,
Thank you so much for getting in touch.
The options are also available in the free version. Just make sure you are in Advanced Mode and not in Easy Mode. You can switch to Advanced Mode by going to Rank Math SEO > Dashboard, then clicking on Advanced Mode at the top right, as shown here:

Once enabled, the Advanced tab in individual posts will be visible, allowing you to set posts to noindex.
For setting a category to noindex, you do that in the Titles & Meta settings or in the editor by enabling the SEO Controls.
Alternatively, upgrading to Rank Math PRO will allow you to use Bulk Actions to set categories to noindex, which provides more flexibility than using code.
Don’t hesitate to get in touch with us if you have any other questions.
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.