Polarization Angle in HFSS

can anyone help me for the above said problem

Insert an incident plane wave. It will ask you for the polarization directions.

What type of excitation are you using? Incident plane wave or floquet ports?

i'm using incident plane wave along with waveports applied on the air boundary(box).

When you assign the incident plane wave, you select the direction of the Eo and Ko vectors. Ko is poynting vector and pick Eo for the polarization that you desire.