Problem with domain

[zainx]

I bought a domain last night with heartinternet and i have never used these before and i dont no where i put my DNS there is an area i thought i should put it but it comes up Error: Your chosen nameservers do not exist in the dns. Nameservers must resolve to a valid IP address.
Can any 1 hu have used heartinternet tell me how to do this?

Edit - Fixed