How configuration Cloudflare on subdomain?

How configuration Cloudflare on subdomain?

Thank you!

If you ONLY want to setup CloudFlare on a Subdomain and not anything else you will have to go for the CNAME Setup:

With this you are able to setup CloudFlare on a CNAME and letting the rest stay how it is.
But this type of setup is available from Business-Level and Up (Business and Enterprise)