reseller nameserver

[Deen@]

I have a reseller who has ns registered with namecheap pointing to two ip's on my server..

lets say the ips are:

1.1.1.1
1.1.1.2


when i ping his nameservers,

ns1.resellerexample.com
ns2.resellerexample.com

it shows 1.1.1.1 & 1.1.1.2


Now

how do i set up his dns in plesk?