Well, the simplest thing is to copy one of the transistors from analogLib (e.g. nmos4). The important thing is the "model" name which can be the name of the subckt (spectre doesn't have the requirement that SPICE does for the first letter of the instance name to indicate what "type" of device it is). You can modify the model name either on the instance of the transistor, or change the default in the CDF (Tools->CDF->Edit in the CIW, remembering to set the type to "Base" to ensure the changes get saved to disk).Originally posted in cdnusers.org by adbeckett
Then you'll need to include the model file in ADE (Setup->Model Libraries).
It's fairly simple, and there are examples of doing this in the documentation, as far as I remember.