How to simulate .gds files in HFSS

I want to do EM simulations on a single process inductance using HFSS, and I've imported its .gds file from Cadence. But I don't know how to simulate it, I'm totally new to HFSS and I've read somewhere that the .gds file is not enough for EM simulation and I've got to add some more information such as thickness and etc. depending on my process. That's pretty much all I know.
I'd appreciate it if somebody could tell me more details about how to simulate .gds files in HFSS. What exactly do I need to add, and how can I do that?

You have to add the excitations (lumped ports or whatever you need), an airbox, radiation boundaries off the top of my head. Start with those and you will get into it!

Have fun!

And of course, you need all the material and layer thickness data for conductors, dielectrics, substrate. GDSII is only the geometry information, and you need to include all the process-specific technology information.