Create Idoc Type under ECC6

Hi folks,

I've created a new Idoc segment for an existing idoc (The original idoc doesn't have the fields I need). I'm now trying to create a new Idoc type taking into consideration the new Idoc Extension I've created. When I type my new idoc type and select 'basic type', I believe I should get prompted (somewhere) to enter the Basic Idoc type and Extension type, but when I create a new basic type, I don't get the option to add my new extension. And If I copy the original basic type, I don't get my new segments.

Can someone please tell me what I'm missing in the create new Idoc Process?

Cheers,

Steve