This depends on what you already have available: if you can use Cadence tools, you should have at least the basic, analog, and (behavourial and functional) vlog & vhdl libraries. I'd copy a cell with an appropriate symbol (with all views) to a new cell-name, then you may still manually edit the symbol. Copy the symbol view to the spectre view. Then edit the schematic; the transistor names and their symbols must point to your SCS model files (if you want to use these models).
This is just a short draft of how it can be done; a lot of details I can't tell you any more: but I've succeeded with it a few years ago with IC5141/MMSIM611.