So how do we compute the pressure term $-\frac{1}{\rho} \nabla p$ in the Navierâ€“Stokes equation? The slides do not seem to give an answer?

So how do we compute the pressure term $-\frac{1}{\rho} \nabla p$ in the Navierâ€“Stokes equation? The slides do not seem to give an answer?