Login to WHM
You can click on "Manage Nameservers IP" and let the system reserve the 2 IPs for you.
However if you want to reuse IPs already used by other nameservers, just go to "edit a DNS zone" and add a few records:
1. Your NS record
yourdomain.com. 14400 NS ns1.yourdomain.com.
yourdomain.com. 14400 NS ns2.yourdomain.com.
(Note that ns1 and ns2 can be anything but must match what you registered in the registrar as nameservers)
2. Your A record
ns1 14400 A 22.214.171.124
ns2 14400 A 126.96.36.199
(Note that ns1 and ns2 must match your NS record in step 1, and that the IPs must match those that you use to register the nameservers in your registrar)
Save and you are done.