Monopole antenna on top of a cuboid simulation using HFSS

Hi! Im new to HFSS. I would like to simulate a monopole which is fixed to a metallic cuboidal support. This support also acts the ground the ground for the system. I would like to know how to assign the cube as the ground. Also, I havent decided how to place the antenna or the clamp that would fix the antenna to the cuboid. Assuming that this clamp is made of a non conducting material, should I incorporate this into the design as well. If not what should I do? Also, I was facing problems while assigning waveports. Could somebody explain the correct method to assign a waveport, integration line and everything. Thanks.