To run Cassandra on multiple cores

Hello,
I am trying to simulate the self-assembly of lipids using the Cassandra. When I am running the simulations they run with long times and so I think only one core is being used in these simulations leading to very long computation times. I wanted to know how should I explicitly mention the number of cores with which I can use to run the simulations. I would really appreciate if any help in this regard is offered.

Thanks in advance