Hi Hassan,
You can do this by choosing a stochastic solver. In the user interface, this can be done by going to the 'Simulation settings' and under 'Solvertype' selecting 'stochastic', 'implicit tau', or 'explicit tau' instead of e.g. ode15s or sundials. See the screenshots below. More on the difference between stochastic/implicit tau/explicit tau solvers can be found here: https://www.mathworks.com/help/simbio/ug/stochastic-solvers.html
If you want to do this programmatically, you can use getconfigset to change the solver. E.g. if your model is called m1:
cs = getconfigset(m1);
cs.SolverType = 'ssa'; % use 'ssa' for stochastic, 'expltau' for explicit or 'impltau' for implicit tau
Let me know if that answers your question.
