converting a general form of PDE to weak form PDE

Hi all ,

I am going to define a weak form of PDE on boundaries of a cylinder based on 4 dependent variables V_m, m, n , h. The following equations need to be converted to weak form but I do not know how to do it. unfortunately there is not any model example or explanation in this regard in comsol tutorial or model library.

equations:

1. d(V_m)/dt=G_Na*(V_m-E_Na)+G_K*(V_m-E_K)+G_l*(V_m-E_l)
2. dm/dt=a_m*(1-m)-b_m*m
3. dn/dt=a_n*(1-n)-b_n*n
4. dh/dt=a_h*(1-h)-b_h*h

could someone help me please??
thanks in advance