3 layer circuit in ADS

I am trying to simulate a three layer patch antenna in ADS. I have used conductor 1 (cond1) for feed netwrok conductor 2 (cond 2) for patch element. Now I want another layer of patch antenna but I dont know which (cond, dielectric, etc)layer to use.....Is there any layer that can be used for third conductor layer

Just define/add another layer in layer editor in Options in ADS.

You need to take care by
momentum --->substrate--->create/modify.

Yep.
you can click to EMDS (Momentum) -> Substrate -> Edit/modify and then you can edit your own new layers, but you should not use < 0.01 um width