design horn antenna. hfss

Hi,

Please help me for getting right results in HFSS:

Q1 how to feed a conical horn antenna and what is the right position to feed?

Q2 what changes should be made in design and material for feeding to achieve appropriate results ?

Q3 how to acheive circular polarization?

Please mention reference of book e.t.c from which you are answering the question.
Thanks & Regards.