Importing a document type in ES

Hi,

I created a document type in IS and exported as a .zip(only one file named node.ndf) file. When I imported this file(node.ndf) in ES, I am getting an error. “The contents of the file “D:\…\node.ndf” are not valid”. (It points to the first line of the file ).
Can anyone tell what’s wrong?

Thanks in advance

RK