The procedure of getting private nameservers is free, and you need to contact your hosting provider in order to get them.
You are to have two dedicated IPs addresses for your private NSs. (most companies require them).
Provide your hosting provider with the names of the NameServers which you want to have as your Private NSs. For example, ns1.<yourdomain.com> and ns2.<yourdomain.com>. The domain <yourdomain.com> must be registered.
After this the Private NameServers must be registered with these dedicated IPs. The registration is performed by the domain registrar
no comments on this as recently it fail me as somehow my all Singapore ISP block it and i saw someone from Turkey also having the same problem (don't know for whatever reasons) and my url forwarding not working. so for those domain in namecheap, i switch to DNS v1 and the rest i change to use another NS server.
namecheap have DNS v1 and DNS v2
FREEDNS are using DNS v2 only.
domain in namecheap have a choice to use either DNS v2 or DNS v1.
as told by namecheap DNS v2 or DNS v1 are 2 different system.