In order to transmit and receive in opposite circular polarities you will need to add the circular tube between the feed horn and the OMT of the VSAT. Assemble the feed so that the receive part of the OMT (which the LNB is attached to) is perpendicular to the ground and the wide face of the waveguide is parallel to the ground. Make sure that the receive part of the OMT is aligned to the desired reception polarity, either LHCP or RHCP which is displayed on the mouth of the circular tube.