The Phase section is only available if at least one physics or multiphysics interface in the model includes a phase.

From the Solution at angle (phase) list, choose From dataset (the default, with the angle from the dataset added), Custom per plot, to specify the phase individually for each plot in the plot group, or Manual, to add a user-defined phase (in degrees) in the Phase field below, or use the slider underneath to specify a phase between 0 and 360 degrees.