Ibrahim,
WE simulation requires the use of stochastic dynamics. For MD simulations, this is typically achieved by using a stochastic thermostat, i.e. a Langevin or Bussi's stochastic velocity rescaling thermostat rather than a deterministic thermostat like Nose-Hoover. So you should use the Gromacs settings for either a Langevin or stochastic velocity rescaling thermostat, including the recommended barostat for that thermostat.
For the choice of coupling constant to use with the thermostat, I suggest that you consult this paper by
Basconi & Shirts.
All the best,
Lillian