How to Replace nameservers

I’ve host domain on InfinityFree, and I register it on Cloudfare, and it told me to replace InfinityFree’s servename to Cloudflare’s. Where can I replace it?

From your domain registrar.
If CloudFlare is your registrar, then you are out of luck

I found it on Whois, but I still don’t know where to edit it…

Just edit from where you bought your domain. Where did you change it to byte servers in the first place?

I create it from InfinityFree :smiling_face_with_tear:

So you are using free subdomain?
If that is the case, you will not be able to use CloudFlare.
Custom domain is needed.
See below for more info

Thank you very much for your help! By the way, I have used the free free subdomain to make the website (sorry, I am still a newbie…) Will it matter if I change the domain?

Just update your website accordingly

ok