If you are using one of x10hosting's free subdomains, you need to activate CloudFlare through cPanel. That way, no nameserver changes are needed because it is not possible to change nameservers for this.
The CloudFlare link in cPanel helps add the appropriate CNAME records so your domain works with CloudFlare. However, for the more advanced features CloudFlare offers, you will need your own domain so you can control the namservers.