In the following example, the accum_0.xci file is the IP you generated from the Vivado® IP catalog. Use the following commands to simulate this IP in VCS:
set_property target_simulator VCS [current_project]
set_property compxlib.vcs_compiled_library_dir
<compiled_library_location>[current_project]
launch_simulation -noclean_dir -of_objects [get_files accum_0.xci]