designing parabolic reflector and it's feeder

hi every body
i want to desine parabolic reflector antenna and it's feeder and simulate it by feko. i have a little time.could you help me please?

what sort of help do you need exactly ? Where are you getting stuck ? Be more explicit please.

i need some tutorial about finding dimension of horn,diameter of it's reflector, & learning to work with feko
thank you very much