The process recommended by steps:
First, in Namecheap , we will need to register those IP s as Nameservers of our domain (sub-domains of type NS ) for this go to " Domain List " then click on the " Manage " button of the domain, click on " Advanced DNS " and then click on the link " Add New Record " here you add the data as follows:
Type: NS record
Host: ns1
Value: 109.163.211.143
TTL: Automatic
This would be for the first record, then repeat the process for the second Nameserver :
Type: NS record
Host: ns2
Value: 91.128.171.98
TTL: Automatic
This would result in two sub-domains: ns1. yourdomain.tld and ns2. yourdomain.tld
Now we should only use these sub-domains as Nameservers :
We go to " Domain List ", then click on the " Manage " button, in the " Domain " section, go down to see the section " Nameservers " there you will have several options, select " CustomDNS " and add the NS that we created before:
DNS1 (or NS1): ns1. yourdomain.tld
DNS2 (or NS2): ns2. yourdomain.tld
You save the changes by clicking on the green check next to the X, and you wait for the changes to spread. This can take up to 24 hours, although personally I have never spent more than an hour.
I hope it serves you.