Locate the parts shown to the left: 2 pieces of tubing, 2 pump valves, 1 return hose gasket, and 1 through-hull fitting.
Insert the return hose gasket in the top of the watering tray.
From the underside, poke one of the tubes through the gasket. This will serve as the drainage back to the reservoir. The tube should protrude 2-4 inches into the water tray for the desired depth of water. This can be adjusted at any point and will vary depending on which root medium is used, type of plants grown, and level at which root medium holder is placed in cylinder. For easier assembly and better prevention of blockages, the end of the hose can be cut at an angle as seen to the left. Also, lubricating the inside of the gasket with liquid will make this step easier.
Place the through-hull fitting into the center hole. Thread bolt from the bottom until finger tight. Insert plumbing tube to the male end of this fitting.
The bottom of the watering tray.
Configure plumbing from the pump which connects to the center fitting. The valves may be adjusted to get the desired rate of flow and amount of aeration. In the lower picture, the hose leading to the right attaches to the bottom of the watering tray.
The pump is purchased separately. An example is shown here. It needs to move the water 3-4 feet and may be obtained from a hydroponics supply store or pet store. The reservoir is also purchased separately. The example shown here is a 20 gallon container designed specifically for hydroponics but you can use just about anything.