How to register main domain and sub domain both

I have a domain attached to netlify. I want subdomain as well to register it.

For example my domain is example.com that connected with one app in netlify. I want to attach another.example.com to another app in netlify. If possible how to do this?

Simply add the subdomain to your site: Custom domains | Netlify Docs

First, ensure you have access to your domain registrar’s control panel (where you purchased your domain, e.g., GoDaddy, Namecheap). In your registrar’s settings, locate the DNS management section and create a new DNS record for your subdomain. For example, create a CNAME record that points “another.example.com” to the Netlify subdomain or site you want to connect.

Next, in Netlify, go to your main app’s settings and add “example.com” as a custom domain. Then, in the same Netlify account, create a new site for your subdomain (e.g., “another.example.com”) and configure its settings accordingly. Finally, add “another.example.com” as a custom domain to this new Netlify site.