Registering an iz.rs domain

We had some credits on my last forum to buy a domain, but since it got banned, and we opened a new one, we had to go for the free domain.

Thre are lots of sites on the Web that offer free domains, but we decided to get one from www.iz.rs since they are from Serbia.

The only problem is that they ask you for a DNS server on wich the forum is hosted.

Here's the pic:

TRANSLATION

Registering a domain

IMPORTANT! Hosting and DNS have to be set before registering a domain, or the registration won't be accepted.

Don't forget to, in time shorter then 15 days from registration, send a domain approval request.

Domain is available. You can register it.
You have to insert a DNS server for selected domain.

So, what must I put in the DNS adress tab?
Is it even possible to have an iz.rs domain for Forumotion's forums?

you should email them to find out how to do it?
anyway try this.

http://www.cyberciti.biz/faq/how-to-find-out-what-my-dns-servers-address-is/