I was trying to set nameservers in my domain administration. There is nothing like nameservers. There is NSSET. I tried to put NS1.BYET.ORG but I got error message

NSSet ‘NS1.BYET.ORG’ not found in registry database.

Thanks for advice!

I have no idea what you are talking about and what that error message means. Try to contact your domain provider, they should be able to make sense of the message.

What domain provider is that?