Suspend the plastic sheeting by the tied rock with ample sheeting leftover on the ground to tuck underneath the cone. This loose plastic sheeting will become the circular reservoir inside the unit. Set up something internally to allow the plastic sheeting to make a round, gutter-like water catchment. In terrain with flat ground and loose dirt, simply dig a round trench. On solid surfaces, make a ring from bricks, rocks, debris, or anything else. Use your weights inside the unit to keep it in place.