Change the nameservers

Hello, I need help; I just registered my domain ( on Cloudflare to get an SSL certificate for my site, but I don’t know how to replace the nameservers ( by that of Cloudflaire. I saw a topic of this kind in the help section, but you didn’t say how to replace a nameservers by another … can you help me and tell me if it’s something else to do after that?
Thank you for your helps!! is your domain? That’s odd, I’m quite sure we own that domain. We use that domain to provide free subdomains to our users.

And Cloudflare doesn’t accept subdomains, only own domains, and we don’t support hosting free subdomains elsewhere.