Hi ethanli,
Steps to use VCS, when you want systemc to be instantiated and used are:
1) First compile the systemC files using syscan and on the top module of system C create a verilog wrapper
-- example say sc_top is the top system c file
syscan < all flags > sc_top.cpp:sc_top
Please note here that sc_top.cpp is wrapped in verilog now with sc_top name, which can be instantiated.
2) use sc_top instance to include in verilog top level, and use -sysc flag on vcs ellaboration to tell that VCS can can expect sysC module inside