how to mesh a horn antenna in feko

I simulated a horn antenna in x-band ferequency at 10.3 ghz
but i dont know how to mesh and i want to find the best global mesh sizes edge length and global length
plzzzzzzzzzz someone help me.

it depend on your structure. According to MoM method some face must meshed lambda/20 but for some meshed lamda/4 is enough..