2 elements phased array antenna

Yes,

Just simulate your antennas and afterwards to go Fields and change the excitation to whatever you like.

yes, just go HFSS\Fields\Edit Sources and assign the exitation amplitudes and phases as you want them. This should be used if you need to include the coupling between the elements.

but an easier way would be to use the array option in HFSS far field setup.

i need to know if POLARIZATION of antenna can be set, if i want HORIZONTAL POLARIZATION

what do you mean by polarization ? this depends on your antenna elements (e.g. vertical dipoles will give you vertical polarization, horizontal dipoles will give you horizontal polarization)

also the polarization has no effect on the radiation pattern (if the elements have the same pattern)

thanks for ur suggestions adel actually i m designing a 2 dipoles phased array antenna i have not enough knowledge about Ansoft HFSS. i just got a pdf document from on of my frnd in which designing of a dipole antenna is metioned i m trying my best but i could not get the desired results, thats why i came here to mention my problem plz help me i shall be very thankful to you