Cloudflare nameservers

How do I switch nameservers from & to cloudflare ones as requested by them? Also, I saw an option in cPanel which allows me to enable cloudflare on a domain, but I get an error:
Please help me fix this

Please see this KB article:

If that doesn’t answer you question, can you please tell me what kind of domain you’re using (subdomain or custom domain)?

I had a free domain before and when I tried to register it using cloudflare website I got a 1049 error code. now I have a domain and when I setup using the cloudflare website, I don’t get the error anymore they asked me to switch nameservers from and to and I don’t remember if it was like that, I will have to check. Anyways, how do I switch nameservers?

Switching nameservers can be done through the configuration of your domain registrar. Note that any domain changes you do through our control panel (CNAME records, SPF, MX records) will need to be done through Cloudflare and domain changes like subdomains require configuration with Cloudflare too.

As for the error code, you’ll need to check that with Cloudflare. We don’t maintain the Cloudflare website so I don’t know what all error codes mean and how to fix them.