The equilibrium phase-change model is set up like any other multi-component fluid (MCF) mixture calculation.
You should select the Homogeneous Binary Mixture as your domain fluid.
On the Fluid Models form, you should select one of the mixture components to be the Equilibrium Fraction and the other to be the Equilibrium Constraint.
Now proceed to set up initial and boundary conditions just as you would for a standard MCF model.
Hint: For liquid-vapor calculations, if you chose the vapor phase, then the equilibrium fraction is the "quality." If you chose the liquid phase, then the equilibrium fraction is the "wetness."