The glue records for the domain name point to the appropriate name servers. It's a field you have to fill in when you register for the domain.
If you do a dig on www.shoes.com, here are the listed name servers:
shoes.com. 172744 IN NS ns5.savvis.net.
shoes.com. 172744 IN NS ns1.savvis.net.
shoes.com. 172744 IN NS ns2.savvis.net.
shoes.com. 172744 IN NS ns3.savvis.net.
shoes.com. 172744 IN NS ns4.savvis.net.
So those are the authoritative name servers for your domain and those servers are where all DNS queries on that domain will be resolved.
When you sign up for a domain, the registrar will ask for your name server address and domain name. If it's a brand new domain, you setup your own name server and call it ns1.yourdomain.com, even though you don't have the domain yet, and give them the IP address for that server.
They'll then configure the glue record for your domain to point to that address. Any DNS queries on your domain will hit the registrar first for the glue records and proceed from there.
Since you mentioned you have a DNS server, you would give the registrar the address of that server and call that server whatever you like but, again, standard practice is to use something like ns1.yourdomain.com
On your DNS server, you need to configure it to be authoritative for yourdomain.com and add the NS entry for ns1.yourdomain.com as well as any other entries you need.
Now, you said you have your ISPs DNS servers configured on your DNS server, and that's probably where the confusion is.
Basically, any queries for yourdomain.com are served by your DNS server itself and that's why you use the address of your DNS server. The reason your ISPs domain servers are configured on your DNS is because it passes requests from your internal hosts over to your ISP for any domains it is not authoritative for.