Zone air distribution units are placed at the zone level. To place an ADU, click on the Add air distribution unit tool and then select the required unit from the drop-list and then making sure that the cursor is inside the boundary of the zone, just click the mouse button to place the ADU. The ADU will be automatically positioned at the top left of the zone:
Note You must also add a zone extract unit to a zone that contains an ADU in order to connect up the air return path from the zone.